LUN-579 : Add layout drop down JS listener

- add onchange listener to make appropriate number of merlin objects visible
- add form submit event to clear previously populated, but not visible, merlin fields
LUN-579 : Minor code improvement
LUN-579 : Add help button for layout dropdown

- Added a help buton next the the layout dropdown that will open a new window displaying examples with available layouts for One Promo smart snippet
LUN-579 : Change displayed image for help button
LUN-579 : Remove logging, fix misspelling
Merge pull request #17 from pbs/LUN-579

Review and integrate LUN-579