Thread pool is not copy constructable

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.

Fixes #2549: ThreadPool that calls progress reporting automatically. This required setting up a base ProgressBase class in Kernel, from which Progress (in API) derives. Added tests for the Progress class.

Refs #2400: EventWorkspace sorting implemented using a ThreadPool. Speed up of about 25% for PG3_1370, for example.

Fixes #2366: Fixes memory leaks (except a possible one involving FunctionTask that seems to be in boost; or could be a false positive).

Refs #2366: Added windows DLLExport clause; more tests in ThreadPool. Simplistic serial implementation for now.

Rename Framework code directory to just that. Also delete Main and VS & Eclipse project file. Re #1881.

Copyright updated to read
Copyright © 2007-10 ISIS Rutherford Appleton Laboratory & NScD Oak Ridge National Laboratory

Allow empty value in ListValidator if it's on the list of allowed values plus a bit of tidying up in the validators.
Re #501.

There are changes to WorkspacePropertys that affect PropertyManager.  In all cases Property.setValue() now returns a string containing any validation errors.  This is a change to the WorkspacePropertys that sometimes ignored errors.  There are descriptions for some propertys in MantidPlot available as a tooltip re #593 and re #410 

Mantid Plot now gives explanations for rejecting parameters!  Let me know if any messages could be more helpful. re #409

Added file validator for properties. Also added a method for getting the type of the validator as a string - could not see an alternative way of doing this. Refs #154

Added validators for properties