bugs: future prospects

[arthurzam]

This will be done in multiple stages, since this is a big thing:

### Stage 2
- [ ] Fix the bugs surrounding `use_dep`. When matching the pkgset, we need to verify confirmation on `use_dep`.
- [ ] https://github.com/pkgcore/pkgdev/issues/131
- [ ] https://github.com/pkgcore/pkgdev/issues/132
- [ ] https://github.com/pkgcore/pkgdev/issues/134
- [ ] Support rekeyword / new keywords https://github.com/pkgcore/pkgdev/issues/123
- [ ] https://github.com/pkgcore/pkgdev/issues/136
- [ ] https://github.com/pkgcore/pkgdev/issues/139
- [x] After user says "Yes" to file bugs, ask if he wants to verify already open bugs. In this case search for bugs with package list, and if found update the bug-dep-graph with the existing bug id
- [ ] https://github.com/pkgcore/pkgdev/issues/154
- [ ] https://github.com/pkgcore/pkgdev/issues/163
- [ ] https://github.com/pkgcore/pkgdev/issues/161
- [ ] https://github.com/pkgcore/pkgdev/issues/125
- [ ] https://github.com/pkgcore/pkgdev/issues/167
- [ ] https://github.com/pkgcore/pkgdev/issues/170

### Stage 3
- [ ] https://github.com/pkgcore/pkgdev/issues/140
- [ ] https://github.com/pkgcore/pkgdev/issues/157
- [ ] https://github.com/pkgcore/pkgdev/issues/129
- [ ] https://github.com/pkgcore/pkgdev/issues/169