Added psq_run_tool_on_source and psq_run_tool_for_each_source

These commands will cause tools to be run as a source-level dependency,
meaning they'll only be re-run if the particular source they're attached
to is updated. They also print a comment out stating that they are running,
which is much more useful then having N long-running tools run over M
source files in the link stage.
Merge pull request #11 from smspillaz/tooling-cmake-util.item_11

Added psq_run_tool_on_source and psq_run_tool_for_each_source