CLA UX Enhancements

 :fork_and_knife: :meat_on_bone: :curry: :rice_ball:

Working on improving the UX surrounding CLAs.

Changes:

- display flash notice below beta banner
- update the agreements content on Manage Profile to be more descriptive (display date and more descriptive button text)
- redirect to ICLA signature and CCLA signature to more useful places
- when viewing an already signed ICLA, display the date and information explaining why one might resign the ICLA
- when viewing an already signed CCLA, display the date and information explaining why one might resign the CCLA
- remove company column from ICLA signatures list
- display name in ICLA sigs list using the signature first and last name to ensure there are no blank names
- change the copy header of Approved Contributors to just Contributors
- remove contributors toggle within companies table and create a separate view for listing the contributors
- remove the company attribute from ICLAs entirely
- create partial w/ permissions for the CCLA Organization nav tabs that is used when viewing a CCLA signature, Contributor management and list of Contributors
- only allow CCLA admins to edit and re-sign a CCLA. non-admins see a read-only form
- display information above the new CCLA signature form that explains the implications of signing a new one! suggest that they look for their company and reach out for an invite. Once we have requesting in, that would replace the current suggestion

Working off of this Trello card: https://trello.com/c/pwYhdIHc

Closes #449 
Closes #434
Seems like the following would be a bit cleaner but maybe it's just personal preference.

```erb
<%= link_to "#{icla_signature.user.first_name} #{icla_signature.user.last_name}", icla_signature.user %>
```