Moved purple_core_init to cython, added purple debug methods, added checks for core...

FIXES:
 - Moved purple_core_init from c_purple.c directly to Cython code. Now only callbacks are done inside c_purple code.
 - Added purple debug methods, so we can use it inside code.
 - Added check for core initialization.
 - Added check to ensure that it has only one instance of libpurple running.

Signed-off-by: Bruno Abinader <bruno.abinader@indt.org.br>

git-svn-id: https://garage.maemo.org/svn/carman/branches/carman-0.7-beta2/python-purple@1273 596f6dd7-e928-0410-a184-9e12fd12cf7e