Also removed outdated mammouth instruction.

- the lock is now properly set in the new compiledir when set_compiledir is
  called after an initial call to get_lock()
- timeout is now 2 mins instead of 1 (safer in case compilation takes a while)
- the loop trying to acquire the lock does not raise an exception anymore when
  something weird happens, because who knows what might happen with parallel
  stuff ;)

(either directly or indirectly) to Module is deprecated.  Just use
Variable."

- The lock should now be properly released even after abnormal termination
- Verbosity of the lock has been reduced while waiting to acquire a lock
- Fixed bug where a job would not be able to acquire a lock when the timeout
  expires

Moved the information about compilation directory from the sandbox to the advanced topic on the compilation pipeline

Compilation directory lock is now disabled again by default, due to lock files persisting after e.g. manually interrupting the compilation