Round robin and FAST search strategies

[sears-s]

Set searchStrategy option to either:

rating (default):

• Original FLUFFI functionality
• Selects testcase with highest rating

or roundRobin:

• Selects testcase that was chosen the longest time ago

or FAST:

• Selects testcase with lowest number of times chosen
• Selects testcase with lowest number of paths exercised
• Selects testcase with highest rating

Implementation notes:

• Column ChosenCounter added to interesting_testcases table which increments each time a testcase is chosen to be mutated
• Column TimeLastChosen added to interesting_testcases table which updates to current timestamp each time a testcase is chosen to be mutated

Relies on #275.