Deletion of tasks implemented.
Foreign keys constraint enabling changed.
Icon of the "Edit" item of the contextual action bar made transparent when the item is disabled.
Method for getting all tags from a context added.
Naming error fix.
Method for setting the ID added.
Method for creating/updating a task tag added. Task data model refactored.
ID is now returned when saving a new element in the database.
Logic for adding tags to a task implemented. Some parts of the code refactored.