Also updated class_maker.py

Apply change to insert export macros into class definition using cmake GenerateExportHeader
feature to 3 more projects: API, Crystal and CurveFitting
Have replaced DllExport with the cmake macro except in these places:

a) class templates - the definitions of class template member functions need to be in the
same unit as the declaration so dllimport gives a compilation error in the client code
(C2491 in VS) eg SingleValueParameter, SingleValueParameterParser
b) headers which are in a project but aren't included by any .cpp units in the project
eg IBackgroundFunction.h, ICatalogInfoService.h. In these cases I've removed the DLLExport
attribute completely

For the API target there were a couple of special cases\extras:

API has some conditional use of the extern keyword to control instantiation of template
classes. This has been inserted into the automatically created dllconfig.h using a cmake
switch that allows some custom content to be appended to the end of the file. Few of the
targets require this so I've added a boolean parameter to the wrapper function to handle
this GENERATE_MANTID_EXPORT_HEADER

I also had to add explicit include directories to PythonInterfaceCore where it imports an
API target header (in the unit ExtractWorkspace.h) without having API as a dependency

This commit replaces all header guards in API with #pragma once

Required to set existing properties from a Json object
Refs #23988

Converts a property object into a Json representation for serialization
Refs #23988

Update copyright headers in all files

Squashed commit of the following:

* First version of a script to manage copyright statements

re #23468

* Neatened up script, added comments

re #23488

* move script to tools directory

re #23488

* small script changes and a couple of manual file changes

re #23488

* Minor chnage to whitespace detection in regex

re #23488

* Add an excluded directory

re #23488

* remove a repeasted copyright statement in a file

re #23488

* Don't comsume the comment end if it is on the same line

re #23488

* fix error in new copright parsing

re #23488

* remove double copyrifght entry

re #23488

* Improve handling of old copyrights at the start of comments

re #23488

* remove empty comments re #23488

* exclude gsoapgenerated directories

re #23488

* Sort out greedy line matching re #23488

* improve empty comment removal

re #23488

* improve false positives

re #23488

* impressive speedup by limiting regex matching length

re #23488

* remove evil invisible non ascii character

Also upadte the copyright at the same time

re #23488

* resolve multiple copyrights in a single file

re #23488

* resolve an issue with new statement detection

re #23488

* another unprintable unicode character

re #23488

* pep updates and cmake the new copyright fit clang format

re #23488

* update already done new format headers

re #23488

* wrong type of bracket

re #23488

* Update class_maker and friends

re #23488

* Update all copyright statements

re #23488

* clang format re #23488

* flake8 warnings re #23488

* Flake8 warnings re #23488

* Exclude .cmake.in and rb.in files

re #23488

* replace missing line re #23488

* exclude .py.in files as they are flasely recognized as C++

re #23488

* another setp.py.in re #23488

* another .py.in correction re #23488

* Hopefully the last of the .py.in files re #23488

* resolve utf-8 encoding of python files and changed ABINS checksum

re #23488

* updates to unit tests that reference line numbers

re #23488

* remaining unit test files and other fixes

re #23488

Update to clang-format-5 and reformat the codebase 

# Please enter a commit message to explain why this merge is necessary,
# especially if it merges an updated upstream into a topic branch.
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# Lines starting with '#' will be ignored, and an empty message aborts
# the commit.

re #15164

Ensures that clone can return the concrete type.

Touches nearly everything unfortunately but is necessary.

Refs #3157 Sort our System.h. It was becoming a dumping ground. It should only be touched when absolutely necessary as it affects every file in Mantid. Also combined this with Refs #2345 to sort out DLLExport/DLLImport usage. It's done for Kernel, Geometry and API but stuff in the plugins could do with updating as well.

Refs #2635. Added AlgorithmProperty class plus a AlgorithmHasProperty validator and some tests. This will allow algorithm objects to be passed in to other algorithms as properties.