[IMP-dev] version and last_modified_by

Two suggestions: First, replace last_modified_by with get_author and version with get_version. Second, define a standard IMP version number and use it for all objects in the IMP kernel. And have a standard author list (or just say "IMP core developers" and give some general imp email address).

We never really bother to update those fields as it is, and for most people the IMP version will be what matters (and for us, the SVN version gives us the information we need).