NEXUS-6574 - add early validation to nexusUrl to prevent common mistakes and vague error messages later
NEXUS-6574 - minor javadoc cleanups for parameters
NEXUS-6574 - slightly stricter nexusUrl validation

- explicit test nexusUrl for https or http URL
- add slash at URL part end for consistency
NEXUS-6574 - remove throws default junk from test methods
Merge pull request #67 from sonatype/NEXUS-6574-nexusUrl-validation

NEXUS-6574 - add early validation to nexusUrl to prevent using the wrong URL