added docs for the user schema feature
added docs about querying user schema tables
add support for using custom schemas
change PartitionName to consider schema names for custom schemas too
correctly handle partitioned table indices and templates
add SCHEMA to non-reserved keywords (according to ISO/IEC 9075)
forbid empty schema on table creation

and streamline exceptions thrown on illegal schema or table name
eliminate concrete doc schema checks

replaced with system schema checks.
also use defined schema at shard expressions instead of hardcoded `doc` one.
upgraded admin-ui to 0.11.0 (including custom schema support)
updated CHANGES
add note about partition name limitations
Merge branch 'user_schemas'