File Module: fine granular locking of update operations

[ChristianGruen]

Currently, global file write locks are enforced for updating file operations like file:write. We could implement a more fine granular file lock, and enforce sequential activity only if a file with the same path is updated. Challenges:

• Operations like file:delete, file:move and file:delete affect more than one file.
• File paths need to be normalized/canonicalized.