Isolate avocado.external.{gdbmi_parser,spark} from being used by test developers.

Move avocado.external.gdbmi_parser and avocado.external.spark
to avocado.core.gdmi_parser and avocado.core.spark, in conformance to
our purpose of keeping things not related to test developers,
inside avocado.core, isolated from users.

After this, `avocado.external` module is gone.
Signed-off-by: NRudá Moura <rmoura@redhat.com>

avocado/gdb.py

@@ -32,7 +32,7 @@ except ImportError:
     import subprocess
 
 from avocado.utils import network
-from avocado.external import gdbmi_parser
+from avocado.core import gdbmi_parser
 
 GDB_PROMPT = '(gdb)'
 GDB_EXIT = '^exit'

setup.py

@@ -108,7 +108,6 @@ if __name__ == '__main__':
           url='http://avocado-framework.github.io/',
           packages=['avocado',
                     'avocado.core',
-                    'avocado.external',
                     'avocado.linux',
                     'avocado.utils',
                     'avocado.plugins',