Fixes Cython compilation errors, minor bugfixes

interface.pyx wasn't linking properly to the botting libraries; after
editiing the Makefile to use the proper flags for compiling and linking
all of our dynamic libraries, it is linked properly, but importing
libinterface.so from pure Python hangs, for some reason. db.* has been
renamed django_db.*, because there is already a libdb.so in the
LD_LIBRARY_PATH, which was causing our libraries to link incorrectly;
rather than deal with system specific configuration, I renamed the
library.
Bot management now functional; fixes segfaults

Bots are now managed using pid's, stored in Django's MySQL databases;
all MySQL-related segfaults have been fixed, and for future reference,
were caused by either trying to extract values from empty result sets,
or trying to store MySQL NULL values for int-valued fields directly into
C int types. Bots can now be managed asynchronously through the
bots::user class, which hooks into MySQL using private db::bot objects.
I also split the Cython interface into what is essentially a header and
source file, and added a main file to test bot management. Minor bugfixes
for db::bot methods.