Expanded use of EntryKind.synchronizable and clarified behavior.
Expanded use of EntryKind.synchronizable and clarified behavior.

This commit replaces a few of our explicit kind class checks with this
newer and more centralized method. It also makes the behavior of the
method more explicit, making it clear that synchronizability is a binary
classification for all entry kinds.

Signed-off-by: Jacob Howard <f862f167b85d41b225785c70d70808bc7337c1fe@havoc.io>

havoc-io/mutagen,havoc-io/mutagen