Remove mode functionality

[knownasilya]

The mode functionality doesn't really make much sense, since measure mode is a subset of certain tools in draw mode, so measure should just be a function of the tool. This way we remove the need for a mode altogether and just have a flag whether that item is showing measurements. This would also allow different units per item, making markup with miles and feet possible on the same map.

This would reduce the cognitive overhead of having multiple result lists and multiple modes.
It would also simplify any refactors to the implementation of the tools.