Reorganized directory structure. Refs #7688.

Modified gitattributes to allow gSoap generated files to be commited.
Updated ICAT3 generated code to latest gSOAP version. Refs #7688.

- Modified `ICatHelper.cpp` as generated attribute name has changed (most likely a bug in gSOAP).
- Increased file size in .attributes to allow `soapC.cpp` to be uploaded.
Added README to assist in future gSOAP usage. Refs #7688.
Fixed include path. Refs #7688.
Added macro to prevent OSX issues. Refs #7688.
Updated README for future reference. Refs #7688.
Fix for OSX issues. Refs #7688.
Updated README to include OSX compiling fixes. Refs #7688.
Improved README file. Refs #7688.
Merge remote-tracking branch 'origin/feature/7688_Reorganise_ICAT_directory_structure'