Integrate the commit checker (and the savepoints checker) in the CI prechecker

2 commits, 1st one is the integration itself. 2nd one are some changes to both the commit and savepoints checkstyle generators to ensure they always are there (no matter they are empty) and produce constant 0-problems hash (we'll be replacing that for some proper counters/exit codes, but not now).

More detailed information in the (correct, lol) commit messages :-)