Feature - Usability of main slider

[JohnRoux]

Currently the main slider is quite a schlep to use.
I get the desire to have an easy to use slider, but having an input field where one can type the amount, is also a really good idea.

Currently the slider is kindof every R10, but sometimes it will skip an increment (eg: R300)

Eg: HumbleBundle's "choose where your money goes" sliders