Ability to specify only desired semver level for -gt or has_update()

[dvershinin]

Most RPM-based auto-builds should only work with minor semantic version updates, because major updates bring API-incompatible changes, and as such aren't very suitable for distros aiming stability.

E.g.

# return success for any version newer than 1.2.3 (default)
lastversion repo --semver major -gt 1.2.3 

# return success for any version newer than 1.2.3 but below 2.0.0
lastversion repo --semver minor -gt 1.2.3

# return success only for version 1.2.4 to 1.2.9
lastversion repo --semver patch -gt 1.2.3 

Returned another exit status code 4 if -gt "failed" due to semver constraints. (so that it is possible to script things like sending an email if major release is out to review whether it should be re-incorporated to build)