Require update type, R or Python

Explicitly request type of update via cli flags: --update_python_exts, --update_R_exts

Update requirements.txt

2.1.1

clean up requirements.txt

root path of easyconfigs fixed

• when working in the esayconfig tree look up the tree to find the base path for all easyconfig
• check easyblock to determine correct repository to search for exts_list
• check for PythonBundle and PythonPackage
• Read R-bundle-Biocondutor dependencies