add setup_perl_environment as Tool Shed functionality
fix c&p leftovers in comments
Introduce utility method parse_setup_environment_repositories.

Use to reduce code duplication in install_util and provides target for unit tests of new functionality. Add unit tests. Add new functionality for parsing out which packages should be recursive runtime dependencies (not implemented on fabric side yet).
Update perl to use parse_setup_environment_repositories.
Add unit test for all existing functionality in td_common_util.create_or_update_env_shell_file
Add new action to create_or_update_env_shell_file for sourcing other env.sh files.

With unit test.
Introduce higher level abstraction for building up env.sh files in fabric_util.py.

Use it to reduced duplicated code in fabric_util.py. Implement unit tests describing this new class.
Pull in dependant R, Ruby, and Perl complete environments at recursively runtime.
Bring in action fix from @BjoernGruening, not included in previous commit.
WIP: Improved InstallEnvironment.