Test for issue #20

[Homescreen] Write test to access and exit edit mode
updated with assertRaises
updated according to code review
replaced assertRaises with assertEqual
improved _delete_app_locator
Updated TODO message
Merge remote-tracking branch 'mozilla/master' into issue_20
Add fmradio into manifest.ini
Merge pull request #511 from zacc/add_fm_to_manifest

Add fmradio into manifest.ini
Merge remote-tracking branch 'mozilla/master' into issue_20
Redesigned asserts due to zac's comments
Merge pull request #411 from AlinT/issue_20

Test for issue #20
Add test_edit_mode to manifest.ini
Merge pull request #516 from zacc/issue_20

Add test_edit_mode to manifest.ini
Merge remote-tracking branch 'upstream/master' into fix_settings_cell_data
Remove failing script step and reinstate logic to handle the dc-warning box