Allow [patch | minor | major | ....] as version for release command

[sstok]

When creating a new release I should be able to use the next "version fragment" automatically
hubkit minor and get the next logical minor version for this branch.

The command already validates if there are gaps so getting the next version should not be a problem.

This should support patch, minor, major, beta, rc and alpha. And increase that fragment.
For beta this means the current beta version is increased, if there there is no current beta release then increase the minor version and set beta to 1.