added plots from ETLOS
working bar chart bins
working set axis with variables and functions
Merge branch 'develop' into feature/plots

Conflicts:
	oecpy/__init__.py
Added plot module able to plot quantities per parameter bin or scatter plots where parameters can be set for the x and y axis.

Other changes
- Astroquantities now have symbols and most units have LaTex Symbols when needed
- some compound units have been added to aq
- new assertItemsAlmostEqual test
added marker size and colour options
Merge branch 'feature/plots' into develop
updated version number, fixed some small bugs with plots and updated the readme with plot examples
Merge branch 'release/1.0b1.4' into develop