Add Until/Count, Use Bootstrap Modal, Bug Fixes

Added an end options section that includes options for never ending,
ending after a certain number of occurrences, and ending after a
certain date. I swapped out their dialog implementation for Bootstrap
2.3's modal dialog, and fixed numerous bugs:
- Initialization the summary before the frequency so that summary can
be set properly during frequency initialization.
- Display the 'Summary' string all the time instead of if the summary
is under 20 characters for consistency.
- Updating the summary and clearing out the validations when the month
view is toggled.
- Unsubscribing from frequency input events when the frequency is
toggled.