fix file watching for real

[cvogt]

last file watching update didn’t work well enough. This now

• rips out barbary watch service as it seems buggy crashing the jvm
• make cbt exclusively write files to watch to a file
• uses fswatch instead watching all files in that file

fixes #428 fixes #419 fixes #418

[cvogt]

this also get's rid of cbt's second last dependency barbary watch service, which I know @fommil will like ;). Only jgit left.