(PUP-3481) Relax the regexp in parse_selinux_context()

The current regexp in parse_selinux_context failed on a seltype with included a '-' character.
Since it was checking for alphanumerics and underscores, the '-' character and everything to the right of it was dropped.

This commit switches the regex in parse_serlinux_context to split the context on ':' characters.

Note that matchpathcon says the user, role, and type shouldn't have spaces, but don't think the regexp in parse_selinux_context() needs to incorporate this.
Merge branch 'master' of github.com:jude/puppet