Big maintenance release

There hasn't been a RAFCON release for quite some time. In between, a lot of changes have accumulated, which is why we have decided to increase the minor version this time. This is also to reflect the greatly improved installation routine. Nevertheless, also some features made it into this release, especially the NotificationBar.

In the past, installing RAFCON was not always very reliable. Oftentimes, e.g. the fonts were not installed. Other problems occurred, when RAFCON was installed in virtualenv. Furthermore, no wheel file was provided. This should hopefully now all be fixed in this release. On the first run, RAFCON checks for missing files and installs them. Separate checks handle installations in a virtualenv. Those and other changes (clear separation between data and package files) now allow us to ship RAFCON also in a wheel file, which should speed up the installation.

The NotoficationsBar (by default) shows warnings and errors that would otherwise only be listed in the LoggingView now prominently in the GraphicalEditor, giving you better visual feedback. You can also lower the level of message to be shown, to include e.g. also info logs. Further improvements were made e.g. to default values: The default name for new states contains the state type and a counter and the default script shows more capabilities of RAFCON. Now, the view no longer jumps when collapsing the left sidebar.

Also the stability of RAFCON is improved with multiple fixed issues. State machines created with Python 2 and Python 3 should now be 100% identical, making life with a version control system easier.