Dirk auto rescale elevation

NB! This pull request is x-referenced: https://github.com/nens/lizard-nxt/pull/218

problem
======
Atm, clients can select a tool to auto-adjust the scale used for visualizing elevation. This tool only works when having the required base layer already selected. This (i) leads to inconsistent UX for the tools (since some of the other tools can work independently from base layers) and (ii) we decided that we want to adjust elevation colour scaling (when having the base layer selected) when you click on the height button.

solution
======
The elevation layer should always auto-adjust it's colours, and the icon to select the tool should be removed.

todo
====
- [x] Find function used for rescaling
- [x] Trigger the function when required
- [x] Eliminate icon for selecting the tool
- [x] Add conditional ng-click to height button (if active, rescale)