hoodie.database(targetDb).add() should allow to pass _id and should not pass through _rev

[espy]

See espy/hoodie-plugin-tutorial#9

Currently, when you pass a Hoodie object back to database().add() to be added as a new object in a different database, _id and _rev are passed through, which causes a { error: 'conflict', reason: 'Document update conflict.' }.

database().add() should allow the forcing of an _id (reported as not working), but always filter out _rev.

[steve21124]

Also error "{ error: 'conflict', reason: 'Document update conflict.' }." when updating existing object on different database like "global-database"