Create a "Sequential" executor

[GoogleCodeExporter]

The idea is an executor that runs the queries (or updates) in the same order as 
they are in the queries (or updates) file. 
The idea of this executor is give the ability of running the exact same test 
many times (probably to different Solr configurations).

Original issue reported on code.google.com by [email protected] on 12 Dec 2010 at 12:17