entd: Add policy signatures

This is a first pass at signed enterprise policies.  A single script is provided that can sign policies and verify signatures.  Another CL will use this script to start the enterprise daemon after verifying the signature.

In the future the signature verification should be baked directly into entd.

entdwife.sh: initial add of utility script to sign and verify policies.
main.cc: check for root-cert.pem, root_cert.pem as a backup.
fix_pkcs11_token.sh: add lcense header.
add trailing / to 127.0.0.1 permission check.

BUG=chromium-os:4621
TEST=gmerge onto device and test with signed and unsigned policies

Review URL: http://codereview.chromium.org/3541011

Change-Id: I5ccfa07697e61b80e389787637e5c6ec7ba32d53