[Maybe merge] 504 map delete links

Closes #504, but does not close #1017 yet.
@wilo99 Could you make sure that the rebase does not clobber your work from [this commit](https://github.com/onaio/zebra/commit/e07a85e39a147f66358009a03a225360e475db66), and which should take precedence?

Notes: added a confirm-modal with some tuning parameters which I hope can be generic to our code.