Fixing typos in schema docs
xsd-fu: Extend C++ support

· Add GUARD property for include guards
· Add SOURCE_TYPE to distinguish between source and header output
· Source paths are relative to the output directory; this is to
  enable include guard generation
· Metadata output is a single target, rather than five separate
  targets
merge develop -D org -I include -E exclude: PR 499 (Code changes for new schema)
merge develop -D org -I include -E exclude: PR 506 (Memoizer: use Location instead of File to represent 'id')
merge develop -D org -I include -E exclude: PR 510 (CellomicsReader: Improve performance of initFile (develop))
merge develop -D org -I include -E exclude: PR 512 (xsd-fu: Extend C++ support to generate headers and include guards)