Replace Directgov rule with mappings

In reference to https://www.pivotaltracker.com/story/show/74044338

The mappings generated as part of [this commit](https://github.com/rjc123/redirector/commit/1e2b9e6fea67ac186fd6cd1ea6ad99cdaab959a5) are based on transition-stats as of 30th June 2014. These are designed to replace the rule implemented to handle multi-surfacing ```dg_\d*``` documents with single mappings (originally for efficiency / certainty).    

For example, [this link](http://www.direct.gov.uk/en/crimejusticeandthelaw/prisonandprobation/dg_070333) is a new mapping designed to replicate the rule that used [this link's](http://www.direct.gov.uk/en/crimejusticeandthelaw/sentencingprisonandprobation/communitysentences/dg_070333) mapping as the authoritative source for the document.