#2 Process hierarchy notation improvement

[Ondrej Macek]

The Process hierarchy notation plugin has to be improved in many ways. Here are suggested several areas of possible improvement and of some new features:
- Improvemet: GUI
- Improvement: modelling pane
- Improvement: extend already existing possibility to link from a process node to a different model
- New feature: possibility to change colors of nodes and to create color templates for models
- New feature: dynamic adding of node attributes
- New feature: modelling using keyboard shortcuts
- New feature: tabular overview of nodes in a model with possibility to edit them

Note for students: Improvements/new features can be developed in one or more project (depends on the agreement)