Add a removeLines method in CppDocument

[narnaud]

We sometimes want to remove a line (most likely based on a QueryMatch).

Would be nice to have a removeLines(RangeMark) method, that removes the query as well as all comments attached to it (either // or /* */).
Also remove the comment on the same line.

Something like that:

// This should stay

RemoveThisLine(); // <- only this line

// This should be removed
RemoveThisOtherLine(); // <- this line + the comment above

RemoveAnotherLine(); // Also remove this comment