Split Edit buttons into two columns

[mstenta]

As discussed in a recent dev call, it might make sense to reposition the Edit control buttons so that they appear in two columns rather than one tall one. There is an issue right now where the buttons overlap with the Snapping Grid control button. This is especially apparent when you select a feature with either the Move or Edit buttons, which then causes the Delete button to also appear.

Additionally, we discussed tightening up the space between the Edit buttons and the Zoom buttons above them, to further reduce the vertical space they all take up.

[mstenta]

Hmm alternatively... in relation to #134 - would it make sense to start by switching these two sets of controls? Perhaps the Edit controls should display horizontally on top (to the right of the zoom buttons) and the Geolocate and Geocoder buttons could be placed vertically underneath the Zoom buttons?

My original thinking was that Zoom, Geolocate, and Geocoder were all related as "map positioning" controls, so I tried to group them up on top together. The same could be achieved in a vertical arrangement on the left, though. And moving the Edit controls to the top, horizontally aligned, with a bit of extra space to the left (between Zoom and Edit) might make sense conceptually as well. Since the Edit controls are only enabled in certain contexts, this might tighten up the map nicely in all contexts.

[symbioquine]

Here's a mock-up I made during the dev call today showing a possible strategy for putting the add/edit controls into expanding/collapsible menus;

[symbioquine]

I've opened a PR with a light-weight fix for the buttons overlapping on small screens that just moves the edit controls up closer to the zoom in/out buttons; #160

I still think there's merit in the idea of condensing the edit controls further though.