Fix #642 Add tests and refactor test_plugins

- Refactor test_plugins to use pytest
- Add new plugin tests
- Add FIXME comment for firewiresrc issue

Related to #619
Related to #484
Minor improvements to framework/test_plugins.py

:lipstick: Refactoring #642
Fixes error at startup for windows missing plugin

Moves get_default_device and get_default_source methods
out of affected plugin Config classes and into the
get_videoinput_bin or get_audioinput_bin methods, so
that no OS-dependent plugin code gets run at startup.

Fix #658
:green_heart: Fix spacing for inline comments
Fix #653 Dialog not hidden on desktop region selection
Fix #663 Selecting a desktop record region does not always work
Fix #650: Resetting configuration raises error when file do not exist
Insert comment on new tests
Add non-functional test functions for click_add_talk, show_save_prompt, and click_talk
Remove unnecessary comments
Added some comment to test_click_add_talk.py
Add singleShot test to test_click_add_talk
Remove whitespace
Comment out glitchy test
Add SavePromptWidget.py file
Add test SavePromptWidget to talk editor
Remove unused modules
Refactor talkeditor save prompts
Clean up talkeditor.py refactor
Refactor new talk window to remove exec_() method