Allow setting coverage minimum on a per-file or per-code-section level

[rklaehn]

Imagine you have a huge project with low coverage and you want to bring coverage up. It would be useful if you could mark sections of code or files with a coverage minimum. Similar to

// $COVERAGE-OFF$
code
// $COVERAGE-ON$

you could have

// $FULL-COVERAGE-ON$
code
// $FULL-COVERAGE-OFF$

for a section you expect full coverage.

My use for this is that I want to mark sections of code as fully covered and prevent somebody from introducing a coverage reduction.

[kitbellew]

@rklaehn would this work: #253

[ckipp01]

Since we do have finer grain control now for single files etc, I'm going to go ahead and close this. If this ever pops up again we can revisit.