Clarifications on api-name, filenames and servers object

[rartych]

What type of PR is this?

• correction

What this PR does / why we need it:

Missing guideline for file names of API definition files, indirect definition of api-name variable.
This PR adds the definition of api-name to Common Vocabulary and Acronyms and clarifies the name of API definition files and servers object content

Which issue(s) this PR fixes:

Fixes #298 #284

Does this PR introduce a breaking change?

• Yes
• No

Special notes for reviewers:

Do we need similar definition of 'api-version'?
JSON format is not currently used in any subproject, should the file extension .json be removed?

Changelog input

 Clarifications on api-name, filenames and servers object

Additional documentation

[linux-foundation-easycla]

• ✅ login: rartych / name: Rafal Artych (1353c82, 2ea01c0, 14df719)
• ❌ The email address for the commit (f09db45) is not linked to the GitHub account, preventing the EasyCLA check. Consult this Help Article and GitHub Help to resolve. (To view the commit's email address, add .patch at the end of this PR page's URL.) For further assistance with EasyCLA, please submit a support request ticket.

[rartych]

Closing due to problem with EasyCLA - fixed in the PR #333