Add multi-tab support using localStorage

[willseward]

Adds a listener to each instance, which listens to a localStorage value, updated during each call to keepAlive.

Adds the following options:

• clearWarningOnUserActivity - added to preserve existing functionality on BS4, since the modal dismissal was not functioning
• useLocalStorageSynchronization - enables or disabled cross-tab synchronization
• localStorageSynchronizationKey - the key used in the localStorage

[iqionly]

Thanks for your work, currently I'm use your project until orangehill update this :)

[khm-developer]

It's working well. Thanks @willseward