Add support for python recipes

- Allow arbitrary flags to be passed in to recipes
- Fetch dependencies

Example yaml and dependency: https://github.com/saketkc/ggd-recipes/commit/0c024a472309e40afc1d2f578bfdc3c63f1d6975
`python ggd.py install misc/sra/sra --cookbook file:///saketkc-ggd-recipes/ --gid GSE49623 --path /home/test/download`

I am running out of ideas to come up with a demonstrable example, and have not tested it without --cookbook, so it probably should not be merged as of now. My idea was to come up with a POC.
I might bump across a more cleaner way to do this, once I am done with exams.