Mozilla-version

Added
* 78 is the new ESR major number

Added
* `GeckoVersion.bump_version_type()` to help mergedays.

Added
* `FenixVersion` support for release or beta style Fenix releases.

Fixed
* Missing requirements in pypi packages

Added
* `BaseVersion.bump()`, which takes care of setting or resetting the right numbers. It's also exposed to child classes. Edge cases are taken into account
* Pre-rapid-release version numbers (like 1.5.0.1) are now supported. There are a few edge cases still unsupported (e.g.: 3.0.19-real-real)
* `VersionType.RELEASE_CANDIDATE` was added to support pre-rapid-release version numbers.

Changed
* `VersionType.RELEASE` and `VersionType.ESR` have their integer bumped, so `VersionType.RELEASE_CANDIDATE` fits in.
* `PatternNotMatchedError` now takes several patterns
* `GeckoVersion` now raises when an "a2" version is created after [Project Dawn](https://bugzilla.mozilla.org/show_bug.cgi?id=1353821) happened.

Changed
* [Bug 1561617](https://bugzilla.mozilla.org/show_bug.cgi?id=1561617): part 3 - FennecVersion accepts 68.X because of the [version.txt of beta](https://hg.mozilla.org/releases/mozilla-esr68/file/59a3b58682a8a2de6bb29834d583d6e59bdf70f1/mobile/android/config/version-files/beta/version.txt).