LMMS step size too large for LADSPA effect values

[LostRobotMusic]

@tresf, @DomClark and I talked about this a bit on the LMMS Discord.

The problem is that LMMS has a set step size that can be restrictive in some cases. For example, if you load up the Decimator, the Sample Rate can be set to 55.0699 or 110.14, but nothing in between.

In lmms/src/core/LadspaControl.cpp, you can see the current settings for knob step sizes. Using FLOATING as an example, the step size is 1/8000th of the range of the knob for logscale, and 1/800th for anything else. After decreasing the step size from 1/800th to 1/800000th, everything worked quite well. The only problem that arose was that using the mouse wheel to change knob values does it by individual steps, so changing values with the mouse wheel would take a horribly long time. Otherwise, there were no negative effects for the UI, and it would be a wonderful change to implement.

What I'm thinking, is that we massively decrease the step size like I did, and then change things so the mouse wheel, instead of changing the value by single steps, changes the value by a specified fraction of the knob's total range. This would have the same outcome as giving the mouse wheel a larger step size in comparison other methods of changing knob values (click+drag, double click then type value, etc.), which will have a very small step size for extra precision. This will allow very precise changes to easily be made to knob values, without any significant changes to UI.