Enable to use test ranges based on execution times

[kgyrtkirk]

I've made some experiments by using maven regexp instead of inclusion exclusion patterns; it works way better - but to make it work it needs some odd infrastructure; which would be better placed(hidden away) into a jenkins plugin.

parallel-test-executor-plugin does almost the same; it right now uses knapsack-s to try to create test batches with similar sizes - the knapsack approach supports only inclusion/exclusion only which has a few drawbacks:

• can't split up a very large testcase; say if we have a testcase which takes 16 hours; but has several hundred cases - it's not split up
• introducing a new testcase will be executed by either all or none of the batches

I would like to propose to add another execution style; which will be producing regexps suitable for maven to run a range of tests.

I think it will be not be that hard to integrate this into the plugin.

Not sure which is preffered more: smaller patches - or the feature as a whole including all the refactors/etc.