Increase min, max values, precision & introduce grid layout

Possible minimum and maximum values weren't big enough for some coordinate systems, e.g. Grauss Kruger, and max. possible precision of 2 didn't account calculations this big either. 

I have also modified the Qt interface: There's now a grid layout that dynamically resizes the number boxes.

![Screenshot](http://i.imgur.com/bBs5GOa.png)