Implemented ability to select theme for the new or edited task.
Added drop down allowing to select the time investment theme in the toolbar.
Implemented task filtering by the selected time investment theme.
Implemented code autogeneration for the new task.
Implemented correct headers for task form and list.
Added enumerate_it gem implementing enumerations.
Implemented TaskStatus enumeration using enumerate_it gem functionality.
Implemented ability to change the status of the selected task and task status color indication.