Add verbiage/help dialogs/tooltips to admin

[michalbundyra]

We should add help information in more locations throughout the admin, particularly to help educate users about APIs and terminology:

• HTTP verbs (e.g., "GET - fetch/read a resource")
• Content Negotiation (What is a "Content Negotiation Selector"? Why should you care about the Accept/Content-Type whitelists? etc.)
• What is meant by the "route identifier name"? how is it different than the "entity identifier name"? etc.

These could be done as rollover tooltips, or pop open modal dialogs.

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Originally posted by @weierophinney at zfcampus/zf-apigility-admin#208