Change how files with no executable lines are displayed in the HTML report

[sebastianbergmann]

A file that has no executable lines is currently reported to have 0 / 0 = 100% code coverage. This is wrong and confuses a lot of people (see #411 (comment), for instance).

Whatever we do for the HTML code coverage report has to be done in the XML reports as well to avoid confusion through inconsistency. This is what #428 is about.

The examples shown below are from sebastianbergmann/money.

Current

Possibility

[MajorCaiger]

What about

• "N/A" for the percentage
• leave the 0/0 in (IMO This could be useful information, especially if the row represents a directory)
• make the row a different colour?

[sebastianbergmann]

@MajorCaiger Good idea.

[sebastianbergmann]

The following cases still need to be addressed: