Implement ToolCommandlet for pip

[hohwille]

Create ToolCommandlet for Pip
Old commandlet:
https://github.com/devonfw/ide/blob/master/scripts/src/main/resources/scripts/command/pip

ATTENTION: This story is blocked by #38 that needs to be implemented first.

See also #352 so we will not isolate pip to its own software/pip folder but accept that it lives inside software/python.
Hint: Pip commandlet will be a simply proxy commandlet (like cubectl) that only delegates to pyhton for installation and will run pip inside software/python on runTool.
Hint: We have created DelegatingToolCommandlet for such "proxy commandlet" in the context of Kubectl. This can be reused here.