Cleanup QuickPost shortcut permissions and delete shortcuts from db when a blog is deleted

[ashiagr]

Goal of this task is to clean up shortcut permissions + test shortcut deletion logic when a blog is deleted.

As part of this PR, shortcuts were deleted from DB and uninstalled when a blog was deleted. 

• These changes were lost with FluxC: SiteStore, PostStore migration (1, 2, 3).
• Also, as part of Android API level 26 updates, instead of using INSTALL_SHORTCUT broadcast, the app now creates pinned shortcuts. These pinned shortcuts have a limitation: 

Even though your app cannot remove pinned shortcuts, it can still disable them.

We should

• Cleanup INSTALL_SHORTCUT, UNINSTALL_SHORTCUT permission from AndroidManifest.
• Delete shortcut for a blog from DB when a blog is deleted from DB on logout.
• (Optional) Disable shortcuts on logout preferably with a custom message about why they're disabled. This is optional as the shortcut will still remain pinned on the home screen and the user will have to explicitly delete them. However, with the disabled pinned shortcut, we can provide a message why they are unavailable now.

[peril-wordpress-mobile[bot]]

	Fails
:no_entry_sign:	Please add a type label to this issue. e.g. '[Type] Enhancement'

Generated by :no_entry_sign: dangerJS

[peril-wordpress-mobile[bot]]

	Fails
:no_entry_sign:	Please add a type label to this issue. e.g. '[Type] Enhancement'

Generated by :no_entry_sign: dangerJS

[peril-wordpress-mobile[bot]]

	Fails
:no_entry_sign:	Please add a type label to this issue. e.g. '[Type] Enhancement'

Generated by :no_entry_sign: dangerJS