Release v2.2.0

After a couple of month I proudly present the new major version of
PLCEdit. Version 2.2.0 comes with a lot of new features and got some
good enhancements under the surface.

The new key features are:
- support for Mitsubishi MELSFOT IEC files
- the function block call model converter

Next the support for infoteam’s OpenPCS has started. First files
of OpenPCS will be accepted as plain text POUs. Later seperated
entries in the file open and save dialogs will be added. The sources
are very clean, so there is only something to do regarding the file
extension management in PLCEdit.