(#1533) - Fix maxlen for files constructor.js and ajax.js
(#1442) - Added doc_ids to genReplicationID.
(#1649) - better skip/limit for leveldb
(#1649) - fix allDocs() limit=0
(#1671) - Document adapter usage in constructor

It's not very clear how to restrict PouchDB to
websql-only or memdown. This adds some more
details and examples.
(1680) - Include .idea/ in .gitignore
(1655) - Make genDBUrl and replicateOnServer both use genUrl
Merge remote-tracking branch 'pouchdb/master' into 1533-maxlen-small

Conflicts:
	lib/constructor.js