release 1.6 of the Mercurial PowerShell Provider

BitBucket project link: http://bitbucket.org/artvandalay/mercurialpsprovider/

After some miscellaneous much-needed code cleanup (moving responsibilities out of the provider class into dedicated subservient classes), I noticed that the calls that return many changesets were running many more hg commands than necessary to obtain the result. The speedup was more than significant enough to justify another release. 1.6 should work exactly the same as the previous release, only faster.