Package Config Improvements

Some minor improvements to configuration of default packages. I also have a contrib layer coming soon, but it isn't ready yet.

### Includes:
- Don't pair single quotes in lisp
- Detect ledger files ending with `.ldg` (I :heart: that spacemacs comes with ledger-mode and fish-mode).
- Add a config variable for disabling packages. (added so I could disable jedi, which was broken for me.)
- Remove broken neotree toggle modification (It errored out on activation for me).
- Ignore the python environment created by jedi on install