Add distinct to active strategy query
Drooms Tournaments CLI is dead (it always was just for testing)
Services redone
Use Set instead of Collection in entities

This enables multiple fetch joins and the Set makes more sense as there
are sets in database (equals and hashCode are based on db id columns).
Convert playground configuration regardless of recursion depth

The playground configuration is eagerly fetched and will always be
available.
Set enrollment status when getting user's tournaments
Fetch playgrounds with unfinished tournaments

The playgrounds in tournament don't change and this way it saves one
query every time the tournament should be inserted.
Remove redundant .gitignore files
Add new client module

One client to rule them all! The new client contains all the
functionality necessary for communicating with drooms server.
There are three modes in which the client can run:
1) interactive (default) - used for user's interaction (registration,
new strategies/playgrounds/tournaments, tournament enrollment). This
part was taken from the old cli module and redisigned a bit. There is a
lot of work to be done.
2) execution - used for running the games on the client machines. Using
GameService interface it gets game queue, executes one of the games and
delivers the results back to server.
3) batch mode - will allow running the same commands as an interactive
client from the command line (e.g. adding playgrounds). This mode is not
yet implemented.