Add merge tools from private forks

[sandybrownlee]

Add two tools developed for analysis of Gin's outputs:

• merge profiles tool. This takes multiple profiler output files from repeat runs and determines the intersection of the hot methods then, for each hot method, the union of calling tests. Also add note about repeating profiler runs to documentation (with point about reboots)
• aggregate random sampler output. Random Sampler output is one line per test. This aggregates to one line per edit; with a count of test passes, total tests run, and total run time