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.
Merge branch 'feature/7688_Reorganise_ICAT_directory_structure' into develop