New ideas

I now decided to build in conversion functions and constants. Currently the idea is to make constants available by pressing the 'Func' softkey followed by the 'Const' softkey (at the moment that softkey is unused). For conversions I will most likely introduce a new mode on the Menu form which will replace the function softkey by a conversion softkey. I also introduced some colours to group related buttons together and make the connection to the respective indication button at the top.