This change is a complete rewrite of fscrypt's Makefile.

The new build rules can be roughly divided into secions:
  Build   - bin/fscrypt and bin/pam_fscrypt
  Linting - gen (for .proto files), format, lint
  Test    - test, test-{setup|teardown}, coverage.out
  Install - install, uninstall, install-{bin|pam}
  Tools   - tools and other bin/* needed for the other rules

As before, "make" builds the binary and pam_module, while "make all"
builds and tests everything (except for integration tests), and "make
clean" removes any generated files.

Also note that this new build system:
  - Doesn't require input_fail.py
  - Properly falis on linter errors
  - Builds everything into the bin/ directory (customizable)
  - Builds all the vendored tools

This commit updates the README and Makefile to get them ready for
external release. This includes adding some common pitfalls, including
example usage, and allowing for tarball creation.

Change-Id: I442338c7aff613a14bae449dbf091bfcaf73ed9d

This commit moves most of the documentation about contributing to
fscrypt into CONTRIBUTING.md and updates the legal disclaimer.

It also updates the README.md to include all of fscrypt's planned
functionality and dependencies. Finally, the makefile is updated to
include more documentation, versioning support, and a different location
for the output file.

Change-Id: Ib7be98d41bc06dd12b02e42addf06e12a940235a

This commit includes the Apache 2.0 License and a README with
documentation on how to checkout the code, some context about Linux
filesystem encryption, and documentation stubs for fscrypt and
fscryptctl. Also adds in a simple .gitignore so we don't commit build
files.

Change-Id: I99d5f936c9d65516119dd58c81cfa95c1e6243c1