Added feature to exclude files from coverage analysis

@Johnlon 

cc---

New system property provides a comma separated list of regex's for the paths to ignore in coverage.
Files matching these patterns are excluded from the final coverage reports.

<scct.excluded.paths.regex>src/main/scala/.*Excluded.*/morepath,other/excluded/path/regex</scct.excluded.paths.regex>
I have tested against my own project and it works for me.

Any matching files are dropped entirely from the reports,

However, I have not been able to run any of the tests in the scct package as I keep getting an errors, presumably to do with my runtime env like the one below.

test-fail: Scala compiler is probably not finding scala jars (catch-22).
Fix paths in InstrumentationSpec:createSettings.