allow editing/deleting waypoints

[icrf2000]

This PR allows editing or deleting existing waypoints. Tap on a waypoint in the list to open a dialogue to edit/delete.

I also slightly modified the layout of the waypoint list to accommodate for longer waypoint names.

[aton1698]

Hi, thanks for your contribuiton!
This improvement looks really good, I was testing it and the functionality is great. But there are some things about the desing. First, could be great to use the already existing strings, and the dialog which appears to edit the waypionts could be the same used in others app functionalities, like in the settings options (pop ups).

It would be awesome if you could make the changes, otherwise when we have a little bit of time we will try to fix it.

Also, you can change the target branch to the develop branch? This because we're using gitflow.

[icrf2000]

Ok, changed to develop.

For the design, I don't know whether I'm able to make it more beautiful. I saw that other parts of the app also use the alertdialog. I know it is deprecated, but I didn't use the more recent technologies, fragments etc. so far and have no experience with them. When I find time, I will look into it a bit.