This caused an issue with nested imports on Qt < 5.9

Runs clang-tidy pass by ref across the codebase to fix-up various
warnings we are seeing in cppcheck

Also updated class_maker.py

This commit replaces all header guards in qt/Widgets with #pragma once.

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 

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Some confusion arose during the last directory reshuffle and
these were missed

In SaveWorkspaces the name of the output file now doesn't change if append is selected. Improve error reporting re #2217

Move MantidQt headers into subdirectories for consistency with framework conventions and simpler build. Re #1881.

Fix SANS SaveWorkspaces problem, the signal in the base MantidDialog was being obscured by SaveWindow's redeclaration re #1747

Load and SaveRKH now have default extensions and the save workspaces dialog updates the filename with the workspace's name re #1747 

Attempt to fix the Mantidplot failure on Darwin by simplifying the code in the region of the error re #1263

There is a new dialog that allows saving multiple workspaces in multiple formats. It's accessible from the SANS GUI under "Save Other". Other controls have been added to the SANS GUI to aid loading files and the interface has been rearranged a little. re #1263