Add support for task-level annotation collections

[horvathaa]

Essentially we will automatically append the same tag to each annotation and support a global view such that annotations with this tag may be viewed at all times no matter what website they are attached to. Current "task" should be viewable at the top of the Sidebar. Task should be modifiable and possibly hierarchical (such that there may be "child tasks" that are appended with their own child task name AND the parent-level task).

[horvathaa]

Moving away from this.