Merge pull request #4 from gsaponaro/populate_OPC

[worldStateManager]: use Vocab instead of string for database fields
Merge pull request #5 from gsaponaro/populate_OPC

[worldStateManager]: fix lists
[change] property name - Vocab to str
Merge pull request #6 from vicentepedro/master

[change] property type - Vocab to str
[worldStateManager]: use string for property names.

See also vicentepedro@8ff7096bda4ad5341295d940363a959d4bf82675
[worldStateManager]: start playback mode; add missing OPC stuff to XML
[worldStateManager]: progress in populating OPC, fix XML