Hi guys!

I liked very much this idea! Do you consider we should remove the icon from the actions on both plugins?

Improved style by preferring camel case identifiers, cleaned wrong comments, changed ClangFormat target to issue a WARNING instead of ERROR in case of clang-format executable not being found, and changed the API on PerProjectConfigPage to issue a signal when the selection of checks change instead of using a QStringList pointer owned by someone else.

Thanks for the comments, guys. I already made most of the suggestions, I think.
About the KConfigSkeleton approach I need to study more to understand how it works. In the meantime, I left the PerProjectConfigPage almost in the same way it was, except for the pointer API, which Kevin Funk suggested to change.
As soon as I understand the KConfigSkeleton enough to reimplement the PerProjectConfigPage I'll submit another patch.