Qlist fixes

@lilvinz and I spent some time with Valgrind, and discovered that Qt's QList container isn't very efficient for iterations. This document gives good background on what's going on: http://marcmutz.wordpress.com/effective-qt/containers/

We changed the QVector to QList, changed the loops from incrementing indices to incrementing interators, and factored out some calls that were being done on a per-loop basis, even though they only needed to be called once. Note: these last are probably optimized by the compiler when compiling release versions.

Tests were done using HiTL.

Before:
![screen shot 2013-05-14 at 11 08 35 pm](https://f.cloud.github.com/assets/1118185/503964/b261c96a-bcda-11e2-9c5d-76789a2bafad.png)

After. Note that processPeriodicUpdates falls from 23% to 10%, and that QList drops off the top of the list, and the QVector entry does not replace it. (FYI, it's at ~2%.)
![screen shot 2013-05-14 at 11 08 28 pm](https://f.cloud.github.com/assets/1118185/503963/b25ce882-bcda-11e2-96b3-e6d06dc09f6b.png)