NEXUS-5472: Smaller fixes and comments
NEXUS-5472: Javadoc and comments
Getting rid of lint warning.

Just by adding type, the lint warning of use of unsafe
or unchecked operation is gone.
Merge remote-tracking branch 'origin/master' into nexus-5472-proxy404
NEXUS-5472: Multiple fixes combo

Those are:
* Added LocalWalkerStrategy UT
* fixed LocalWalkerStrategy, as nexus may leave empty folders on artifact removal (it does not enforce remote folder removal when delete over REST or UI the given file, but tasks like snap remover DOES delete empty parents) and it was gathering folders too, hence, creating "false" WL entries even if folder was empty, artifact not present, it was added to WL. Now, _files_ are scanned (downsize, walking will be slower!), but real content is added now to WL.
* aligned hosted repo WL creation (walk) and maintenance (offer/revoke), as the two was falling apart (deploying created full path lists while init or delete+update of WL created capped depth list). Now both behave same, as this is fine as only hosted repo WLs are maintained by Nexus
* separated local and remote scrape depths for real