New convenience features, better feedback and a lot of internal refactoring

At i3logix we have been using Akrabat for the setup and tear down of our database automated tests. Based on our experience, we came up with a bunch of features that would make our life easier. Credit goes to David Stockton (https://github.com/dstockto) for most of the new feature ideas.

* Added more verbose feedback when upgrading or downgrading to a version that doesn’t exist.
* When downgrading, will attempt to set the correct version number
* Change updateTo to accept some magic parameters:
 - next
 -  prev
 - +N (e.g. +1, +5)
 - –N (e.g. -1, -5)
 - Both the following are because of a bug in Zend_Tool - http://framework.zend.com/issues/browse/ZF-11808
 - minusN (e.g. minus1, minus5)
 - zero
- Added the following new commands:
 - next – Will move the schema version to the next migration
 - prev – Will move the schema version to the previous 
 - inc – Will increment the schema version by the passed number of steps
 - dec – Will decrement the schema version by the passed number of steps 

I’m happy to make any adjustments, just let me know.