(#2331) Remove darwinports pkg provider, replace with rewritten macports provider

• Employs port -q installed, much faster than port list installed
• Handles upgrades correctly now
• Makes use of internal port revision for ensure => latest upgrades
• Versionable, now works with ensure => specified_version
• Does not handle port variants at all yet.
• Does not allow manual specification of revision, only version
• Test coverage expanded using newer syntax

Paired-With: Daniel Pittman