Add support of cppcheck static analyzer

It it useful since cppcheck catches different set of errors comparing to clang static analyzer.

Main requirements:

• automatize and provide user friendly generation of cppcheck's command line options;
• perform "on-the-fly" checks of currently opened files (with some obvious limitations like checking only saved files);
• show found issues in issues pane or via text marks.

It should, likely, be implemented as a separate plugin to allow easier addition of other static analyzers.