The only reason it was in the engine was so it could be used by both
the client and the web extension, without worrying about the
webkit2gtk and webkit2gtk_web_extension packages conflicting. However
it didn't really belong there, and added a dependency for the engine
on javascriptcoregtk which doesn't belong. So this fixes all that.
Some software like the above will mangle From mailbox names by appending
"via Some Service" to the From mailbox name. This messes up generating
default avatars for the actual people sending these messages, so
attempt to de-mangle the names.
This involves moving primary originator determination from the engine
to the client, since it's now a policy thing. Add unit tests.
Don't try to dray null initials, actually return null per API contract
when no initials can be found, don't include non-alphanumerics in the
initials. Add test case.
