Fixed another spurious CBLDocumentChange.inConflict value

The logic for setting inConflict in -forceInsert:… was broken. It needs
to check whether the local revision it's going to add a child of is
currently a leaf or not.
Fixes #243.
Return 501, not 404, on JS view query if view-compiler isn’t installed
Improved the ordering of KVO notifications sent by CBLReplication.
Implemented CBLQuery.startKeyDocID, .endKeyDocID

As well as the corresponding REST API.
Fixes #111
Support POST to _changes

When using WebSocket, instead send the options in a JSON message after
opening the connection.
Fixes #110
Router: GET /db/doc?attachments=true should default to multipart

For compatibility with CouchDB. Same goes for ?open_revs.
Fixes #100
Router: Added "vendor" property to GET /
DDData should be compiled into CBL itself, not listener

Fixes #246