#179 Model Editor - improvements and some bugs

[Matthias Filter]

There should be a comment field creating the connection to the DB comment field that explains the quality score.
Changes in the quality score seem to be not be saved
In case of combined primary and secondary models there should be an option to put comments and scores that are related to the whole model and not to distinct "components", as it is the case right now.
It seems in part not clear what else is renamed if a new "model name" is given

[Matthias Filter]

Additionally:
- the Model Editor does not support units for pH and aw
- the Model Editor ignores any additional condition, that has been added, e.g. via the Data Editor

[Armin Weiser]

• comment field added
• quality score is saved now
• model editor already had units for pH and aw ("Dimensionless quantity")
• please check again "Model Editor ignores ...". Firstly, replace the old node by a "fresh" one.
• The "whole model"-part is still open, right?

[Matthias Filter]

The GUI needs some further improvements, so I leave this ticket open for 2.0