NEXUS-5511: Refine reasoning.

With initial change, while all the requirements were added, still
the report for "auto routing rejected", "proxy mode rejected" or
"request is local only" cases all fell under same generic reason
for INFex: "Path %s not found in local storage and remote storage
access is prevented of %s repository."

This change now refines these cases too, as there is always
proper reason "why not".

Also, simplified code, as shouldProxy boolean actually became

shouldProxy :== noRemoteAccessReason != null

Redundant boolean removed.
NEXUS-5511: Make repo ID be in all messages.
NEXUS-5511: Unified repository presence in messages.

Removed used of RepositoryStringUtils.getHumanizedNameString
NEXUS-5511: Reasoning repo appearance unified.
NEXUS-5511: Applied Ben's comment and cleanup.

Such as removal of punctuation
Merge pull request #847 from sonatype/nexus-5511-refine-reasoning

[REVIEW] NEXUS-5511 Refine reasoning