compiler: bulk rename stdgum to libgum in all places

autocorres: remove the submomdule and use the release

update readme, tests, etc. accordingly

regression: lemma and travis cover most tests (minus huge proofs)

* add some isabelle related tests back to lemma-regression
* update libgum typecheck test
* fix isabelle tests
* fix bilby build (fail due to kernel compatibility)
* other misc fixes to test script

[skelfs] Skel-fs framework.

Add entry and exit functions to the various `super_block`, `file_operations`
and `inode_operations` structures.
The idea is to provide a framework of sorts that can be used to implement an
actual filesystem, by implementing the missing pieces, with the grunt work
already done.

This commit also adds support for verbose mode for Makefiles.

Initial Release