Favor charmworldlib over charmstore.py

- Removes early versions of CharmStore which later became charmworldlib
  - Fixes [lp:1273312](http://pad.lv/1273312)
- Removes urllib3 dep making python3-amulet safe to build on precise [lp:1269000](http://pad.lv/1269000)
- Deprecates charmstore.py in favor of charm.py (to be removed after next release)