fs: Filter redundant event in FolderWatcher

Checking modified and renamed bits seems to handle all changes without them being triggered too early/multiple times
Implement Maker

It runs make once to get an initial build, and monitors all source files after that, launching make again as necessary
Makefile improvements

Suppress default suffixes and built-in rules to speed up make
Add /usr/local/bin to PATH
Load all data files from build/data, use Maker to keep them up-to-date