documentation feedback from committee meeting

[denis-yuen]

There were the following questions from the steering committee meeting that should result in documentation improvements

• the docs might reference Docker specifically at times and do not make it clear that we believe that the standard as it exists should support Singularity and other Docker alternatives
• should emphasize that this is a standard for computationally actionable tools, this is different both from a simple unformatted list of tools, but it also means that this is a standard for registries to implement as opposed to a registry implementation itself
• Highlight 4053fcd which describes our process for guaranteeing ID uniqueness when exchanging tools

┆Issue is synchronized with this Jira Story
┆containerName: GA4GH tool-registry-service
┆Issue Number: TRS-28