Document design decisions during bug mining

[Greg4cr]

JxPath and Cli use non-standard target names like "compile-test" instead of "compile.test". I chose to do a string substitution on check-out to change the non-standard names to those expected (done this way because other URL strings needed to be corrected anyways). In other projects, these non-standard names have been handled directly in the build file.

We should document these sort of design decisions, so that - as a group - we can form consistent policies for bug mining. This will make it easier to get new contributors up to speed and to ensure cross-project consistency within Defects4J.