Polish
Polish embedded REPL shell
Drop jumping into shell when running without args

Change SpringCli so that running without arguments no longer jumps into
the embedded REPL shell. This restores the ability to obtain quick usage
help by simply typing `spring` from the command prompt.

Windows users or developers that prefer the embedded shell can still
launch it using `spring shell`.
Polish
Add groovy to dependency management
Resolves #127: Prevent duplicate report outcomes

The collection of outcomes is a list. Sometimes a race condition causes to instances
of the same outcome to get added to the list shown in the report. By replacing this
with a set and propery equals/hashCode, duplicates are prevented from appearing
in the report.

I added test cases to prove that that POJO is properly managed inside a Set and also
to show that duplicates don't appear in the final report.