allow aborting intent execution

[JarbasAl]

• patch to allow aborting an event handler mid execution
• patch to allow aborting get_response mid execution

[JarbasAl]

test with https://github.com/JarbasAl/skill-abort-test

test 1

• say "test" and it should go into a loop saying "i'm here"
• send a bus message "mycroft.skills.abort_execution" and confirm the full intent is aborted
• intent should abort and say "I am dead" logs should have

test 2

• say "test again" and it should go into a loop using get_response, "this is a question"
• send a bus message "mycroft.skills.abort_question" and confirm get_response is aborted logs should have

[ChanceNCounter]

Tested working, but not analyzed.