get rid of special self presence object and incorporate that into roster
Initial XEP-0191 support functions
Add unblock logic
Add block/unblock context menu item
Make sure block list is fetched after features
Fix unblock dialog message
Add block/unblock menu to conversation

Add ability to set a callback on all block/unblock methods
Add snackbar for blocked contacts
Add dynamic tag for blocked contacts

Add missing OnBlocklistChanged callback interface
Unblock contact by clicking on the `blocked' tag
Hide snackbar button while waiting on blocking

Make sure options menu gets updated
Retab all files touched by the XEP-0191 impl.
Cleanup tag creation
Remove some useless imports
Revert "Unblock contact by clicking on the `blocked' tag"

This reverts commit 8dc0bc0200b9cc7d4b93f9cab178b74e5a0da26e.

Conflicts:
	src/main/java/eu/siacs/conversations/entities/Account.java
	src/main/java/eu/siacs/conversations/entities/Contact.java
	src/main/java/eu/siacs/conversations/entities/ListItem.java
	src/main/java/eu/siacs/conversations/ui/BlockContactDialog.java
	src/main/java/eu/siacs/conversations/ui/ContactDetailsActivity.java
	src/main/java/eu/siacs/conversations/ui/ConversationActivity.java
	src/main/java/eu/siacs/conversations/ui/StartConversationActivity.java

See discussion on pull #796
Refactor blocklist iq get packet generation

And make things final... it's like a disease.

See discussion on pull #796
Refactor on blocklist UI update callback

See discussion on pull #796