Update to urgentMail v1.5

This release includes:
- A major improvement to both user settings restore from storage as well as storage of the active settings.
- The Account-checkboxes (added in v1.4) now show as partially selected if at least one folder of the account is selected, and as fully selected if all folders are.

# version 1.4
## new features added with this release
- account-wide checkbox, to select all folders of an account
- improvements to options page. indent subfolders

## bugfixes
- deleting a toplevel folder may lead to lost settings on startup

urgentMail v1.3
* adds multi-level folder support

Changes in version 1.1
* settings are now saved automatically as they are set.