JModelica compliance check and some code cleaning

There are two main changes in this pull request:
- added functionality for compliance test of the library with the JModelica compiler
- streamlining some parts of the code (mainly removing double _ to improve readibility and use, and replacement of the Data() class by a dictionary.

The functionality for JModelica compliance checking is embedded in the Tester class.  It can easiliy be extended to include initialization and even simulation, but it explicitly avoids the use of the .mos files because some libraries do not have .mos files for the example models.