Add minimal About page/documentation including ToS

[pombredanne]

This would be needed for going live.

• This should be an About in the top bar just left of the version and that would display simple text like the about in https://github.com/nexb/vulnerablecode
• The about text should also provide an email to ask for an API key to access the API for Add API rate limiting #460 (comment)
• We need minimal contact info or it could be in the footer #923

[johnmhoran]

About info added 1 or 2 days ago in push to #847.

Re (1) about text should also provide an email to ask for an API key to access the API and (2) We also need minimal contact info or it could be in the footer, I'll implement as soon as someone provides the desired text, email address, contact info etc.

[johnmhoran]

@pombredanne Re the About text and the need for API key instructions and minimal contact info, this is what the new About currently looks like when the user hovers over About in the navbar (as discussed, this comes from the upper-right corner of the GH README):

[pombredanne]

This About is fine. Thanks!

[mjherzog]

We need to define the TOS and criteria for providing API access before not after.
We would need a way to confirm identity and contact the user when there are issues.

[pombredanne]

See #923 for details and follow up.

[pombredanne]

I suggest this footer:

VulnerableCode is free software by nexB Inc. and others | Source code license: Apache-2.0 | Data license: CC-BY-SA-4.0 | Terms of Service

Terms of service should link to a file saved in this repo and we should ensure that the ToS tells clearly that they apply to nexB-hosted VulnerableCode instances.