Modals persist after navigating using forward/backward browser controls

[sfount]

This applies to any of the modules that currently use $modal. Whilst this may not be a common use case it completely breaks the application as the modal controllers and state are preserved (allowing you to continue using the trial balance anywhere in the application for example).

Unless there is a generic solution, modules may be individually responsible for breaking down modals on navigation.

Steps to reproduce:

1. Login
2. Navigate to posting journal
3. Open a trial balance
4. Press the back navigation arrow in the browser (top left in Google Chrome)

Expected behavior:
Modal is removed when page navigates back to home page

Actual behavior:
Modal persists over home page - allowing the user to continue working with the now redundant trial balance

[jniles]

A quick google reveals this ancient workaround (2013!). Should we give it a go, or keep looking for something more elegant?