Reorganize JSON parser with 3-layers event based parsing:
- occi_scanner_json.xrl for syntaxic analysis
- occi_parser_json0.erl for JSON structure
- occi_parser_json.erl for OCCI JSON semantic

They all used common functions from occi_parser.erl for building the chain and such
Update occi_category_mgr API
User mixin addition ok.
Fails retrieving collection of user defined mixin
Fix user defined mixin collection retrieval