[Cpptool-develop] Added line based text document

[Baptiste L. <gai...@fr...>]

    I added a LineBasedTextDocument which adapts TextDocument by converting
index based source range in line/column based source range.

    It still need more testing though, but it can be done. This means that
SourceLocationRange & SourceRange will probably change to ASTNodeRange and
int, which will make thinks somewhat easier for us.

    Baptiste.