Expand Name validator to dependency and relationship tracking

We can extend the application of the package name validator to the dependencies (i.e. depends and makedepends).

Validators for optdepends are different, as they may contain : and other arbitrary characters in the description part of the respective optional dependency (the string right of the :).

Validators for relationships (i.e. conflicts, provides and replaces) are also slightly different as they may contain comparison operators and version chars.