Color-code SQL query "Timeline" stripes according to stacktrace

The changes colour the "Timeline" column of the SQL query panel with each colour determined by the stacktrace.  (The nth unique stacktrace is assigned the nth colour in sequence.)

Two images are attached (1) sample view, and (2) the output of the colour sequence algorithm.

![screen shot 2014-02-08 at 6 16 42 pm](https://f.cloud.github.com/assets/41852/2118755/faa8d9ee-911d-11e3-84ba-71042a663577.png)
![screen shot 2014-02-08 at 8 06 50 pm](https://f.cloud.github.com/assets/41852/2118757/22070e02-911e-11e3-8fc6-18705b5b149e.png)