#31: introduce devon CLI with plugable commands, increase UX, reduce script confusion

[hohwille]

This PR implements #31 improves OS support (#25) and also fixes the following issues:

• Proper fix for dirname in env.sh #23
• Improve handling of environment variables when IDE is configured multiple times #27
• maybe some more I forgot to mention.

[hohwille]

This PR is introducing 3rd party libs for ide-configurator.
IMHO we should avoid using maven-shade-plugin or maven-assembly-plugin to generate a fat jar as this has some license implications. Then the JAR contains a mixture of classes from different vendors and with different licenses. Instead we should keep the ide-configurator JAR free from 3rd party classes and simply add these as their original JARs to the scripts package release. There we can include a TERMS_OF_USE and/or LICENSE file explaining the used licenses. Downloading and including the relevant licenses could be automated with the license-maven-plugin

[hohwille]

To complete this I see the following aspects:

• remove further console variant scripts for windows
• create a command plugin for opening console windows for different OS and types (devon console or devon console cygwin/devon cygwin, ...)
• Add a setup script in the toplevel directory that can be double clicked. What would people expect? Should it also open the IDE (IMHO no) or just setup? Should we still create eclipse-* and vscode-* scripts by default? Or will all users pickup the new CLI approach? IMHO to catch up with our large user-base the toplevel script should create the IDE launch scripts for the main workspace automatically. Then we will have less questions. People can still delete the scripts and use CLI only if they like.
• Adopt IDE scripts to create *.bat files to launch IDE on windows instead of bash scripts (5 minutes of work).
• Integrate devcon?
• Add lots of documentation...