Integrate CobiGen CLI as commandlet

[hohwille]

It will be a big thing but we definitely need to integrate CobiGen into devon-ide and our new CLI. I leave this issue to the experts from the CobiGen team...

[hohwille]

See also #84

[hohwille]

This issue is not complete. Usually PRs should come with code AND documentation.
However, #273 only shipped with cobigen commandlet.
The documentation for this is still missing.
It should be fine to like to the CobiGen CLI documentation but we at least have to create a small AsciiDoc for the cobigen commandlet and link it from the list of commandlets.

[hohwille]

To not block the progress I already merged #273 but also wanted to note that we define a variable for each tool to configure the exact version. This is helpful to allow (large) projects to exactly pre-define the version of the tools used in their devonfw-ide installation. It might be that CobiGen drops support for Java8 and a project still needs to stay on Java8 or the latest CobiGen may be shipped with a bug. Having no way to control this does not meet the goals of devonfw-ide to allow stability and freedom for the projects.
We need an additional PR that will honor an optional COBIGEN_VERSION variable (just analogue to all other commandlets).

[hohwille]

Further, the current approach with doDownload is a hack.
It will not support software updating. You would need to rewrite the entire logic to be able to detect the currently installed version and compare if a newer version is available.
IMHO CobiGen has to provide the CLI in a completely different way as *.tar.gz file with executable Flags and such that it contains what needs to be in the software folder to be fully functional.

cg -h
Error: Unable to access jarfile /Users/hohwille/projects/devon/software/cobigen-cli/cobigen.jar

[hohwille]

Considered done. Created #340 for the remaining issue discussed above.