#847: #826: fixes

[hohwille]

Small fixes and improvements to changes from #826 and part of #933:

• when extracting doUpdateMirrors I also extracted the mirrors_dir variable what caused some confusing errors discussed in available-versions for java invalid #933 - see PR #878: default version from mirrors #893: version prefix #940: generic doInstall #934 that will receive an upstream fix with this PR after merge.
• when devon «tool» version list is performed or devon «tool» version set latest is performed, the mirrors git needs to be cloned and up-to-date what was missing in List available versions for a tool #826
• after devon «tool» version set «version» I now output a hint to the user to run setup to actually do the installation

[hohwille]

How come that the build of this PR is green?
The function doUpdateMirrors will be added in PR #934 and is missing here.
Therefore test-function-doc should fail.
Shouldn't shellcheck also notice this and break the build?

[hohwille]

Documentation of functions and function declarations are in sync.
Awesome!
[SUCCESS] Succeeded running test #0: test-functions-doc

OK. It has been vice versa:
doUpdateMirrors was called but not declared. As it was not declared the test did not fail as no declared function was missing in the documentation.

The question is if we can detect if some do[A-Z].* is called but never declared.

Update: I created #939 for this idea.