Introduce a function for providing the current version of WSUWP

This combines both the platform version and the WordPress changeset
so that it can be used to break various caches when required.
Add docs to the global versioning function
Introduce a section to site-info.php for moving sites

Some option will be provided here to allow a site to be moved to
another network.
Prepend to the table of options rather than being a stranger
Display a table row with a drop down menu for network
Display a drop down of all networks with the current selected
Hook into admin_action_update-site to process site move
Make the requested site change on a submitted form

Some strange behavior still needs to be resolved. We should also
clear cache and redirect when this happens as the admin page we
return to is no longer valid.
Redirect to the sites network admin after saving changes

If we don't redirect, then we're trying to load a site edit screen
for a site that doesn't exist in this context.
Provide a description for moving sites between networks
Merge pull request #96 from washingtonstateuniversity/feature/site-move

[PR] Introduce admin controls for moving sites between networks