Renamed Task to TodoItem
Cleaned TodoItem tests
.completed you can set and get it.

PASS: agent_server.TodoItem.completed you can set and get it.
PASS: TodoItem.repeat you can set and get it.

PASS: agent_server.TodoItem.repeat you can set and get it.
PASS: agent_server.TodoItem to and from json
PASS: agent_server.TodoCollection.fromJson()
PASS: agent_server.TodoCollection.toJson()
Maid TodoColection into a object.