use json in put command
do_export(): check if file exists
show uri for `show collections` command
fix comment
fix typo in `put` command
collection.meta property added
extend key length for sqlite based databases
key length extended up to _KEY_LENGTH
refactoring, use _prepare_key()
_prepare_key to BaseCollection.prepare_key()
prepare_key in delete()
metadata support added
added collections details from database metadata
many kv in put()
many kv in put()
docs refactoring
docs refactoring