Remove the company attribute from ICLA Signatures.

When the ICLA is signed, the user's company matters not.
Update CLA flash messages to be consistent.

Make the CLA flash messages regarding signing, resigning and not being able to
sign a new one more personalized and consistent with the rest of the app.
[WIP] create authorizer methods for CclaSignatures

spec for this are net yet passing - adjust the new ccla signature authorizer
spec to pass.