Use DBMS' lower() function for switching to lowercase wherever possible (supports utf-8 and faster than mb_strtolower)

Superglobals are automatically decoded. Decoding them again could be a
security issue.

Functions that call Group::tagCloudData() expect an Exception on error,
not a Boolean false return value. Fix the method to again throw the
Exception. Leave the try...catch block in it to make the thrown
Exception obvious.

Instead of returning a white screen of death with an uncaught exception
message, omit artist information from the XML document when the artist
of a loved or banned track can't be found. This should also resolve
issue #209, though a more thorough analysis of the cause should be done.

Also remove a stray echo statement in nixtape/users.php.

Server::getRecentScrobbles() doesn't throw anything (it returns null on
error), so there's nothing to catch and nothing to throw. The
conditional statement following that call was also updated accordingly.

All Nixtape views now catch Exceptions thrown by the User class's
constructor.

In most Nixtape views, code that instantiates User objects is now
encapsulated in try...catch blocks.

All code instantiating Artist objects has been encapsulated in
try...catch blocks. This should help solve some potential problems with
invalid artist names.

This should resolve issue #246, though a more thorough analysis of why
the artist isn't found in that case would be nice.

phpDocumentor's @return tag syntax is:
@return datatype description
@return datatype1|datatype2 description

Make popular artists cloud based on loved tracks (removes the need for a cronjob to create it from scrobbles)

committer: Mike Sheldon <mike@mikeasoft.com>