Convert song data structure from array to dictionaries.

It makes the code using the song objects much more readable and
it should be easier to add new fields to song objects.

Signed-off-by: Peter Tworek <tworaz666@gmail.com>
Server: Get rid of mongoose based webserver implementation.

Libevent is simply too good to limit it's usage just to web server
specific code. I plan to use it also in other parts of basileusd. As
a result maintaining separate webserver implementation which will
require libevent anyway does not sound like a great idea.

Signed-off-by: Peter Tworek <tworaz666@gmail.com>
Update TODO file to reflect current status.

Signed-off-by: Peter Tworek <tworaz666@gmail.com>