Simphony-osp

Minor sql and backwards compatibility fixes.

- Support for reasoning via Wrapper: https://gitlab.cc-asp.fraunhofer.de/simphony/wrappers/factpluspluswrapper
- Updated serialization and sql database schema
- Data is now internally stored using rdflib, serialization uses json-ld
- Updated docstring style to google-style
- Allow to set pico install dir via environment variable: OSP_ONTOLOGIES_DIR
- Allow to install dcat and foaf (experimental)
- Bugfixes

Bugfixes when working with EMMO

- Added the yaml2camelcase to convert the entity names of yaml ontologies to camel case.
- Fixed ontology2dot
- Updated an example with postgresql
- Fixed a bug when trying to clear an empty database
- Improved error messages of pico
- Add easy way to serialize CUDS objects: osp.core.utils.serialize / desierialize
- added method to delete cuds objects recursively and fixed a bug that made this impossible
- Cleaned up source code files
- Fixed utils.getrdfgraph
- default relationship can now refer to different namespace

OWL is now integrated in osp-core.

Use `pico install emmo` to install EMMO. To integrate your own owl ontology create a file similar to osp/core/ontology/docs/emmo.yml.

Small example:

>>> from osp.core.namespaces import math
>>> math.Numerical.attributes
{<OntologyAttribute math.hasNumericalData>: None}
>>> x = math.Numerical(hasNumericalData=12)
>>> x
<math.Numerical: c11cc272-cdcf-421a-8838-5f177b065746, CoreSession: 0x7f1987173190>
>>> x.hasNumericalData
12


The changes are mostly backwards compatible, although you will probably get some warnings. To get rid of the warnings:
- `from osp.core import namespace` is now `from osp.core.namespaces import namespace`
- In the YAML ontology, the entity names need no longer be ALL_CAPS
- If you reference entities from code, you have to match the case of the entities as defined in the ontology.