Removed unnecesary + sign
Added capability to retrieve the whole tree

With the parameter ?fulltree=true the complete tree structure for a given
artist is returned. That is the artist info, plus albums and tracks. No scraped
information is retrieved to avoid a DoS to the scraped websites.
Added fulltree documentation
Better exception handling
Replaced prints for logging calls
JSON structures require the attributes to be quoted
Bugfix: self missing
Pylint complaints
Indexer does not print
Moving stuff around