Shrimp Shader Generator FLTK2 GUI (SVN)

ENH: split shader blocks inthe rendered scene, $(shaders) now comes with the surface_shaders, displacement_shaders, volume_shaders and light_shaders variables

drag no more do a selection only highlight the block, for selection LMB.

mouse over block & left mouse button click = block selected
mouse over empty area & left mouse button click = deselect all
mouse over empty area & ALT key pressed = move scene (needed to prepare region selection)

Continued tweaking input pad text.

mouse over block = block outline in "hover orange"

mouse over block = block outline in "hover orange"

mouse over block = block outline in "hover orange"

Missing type_parent in transform() block.

Tweaked fractal headers, it's more useful to have lacunarity, gain, and offset on fBm, Ridged, VLfBm, Turbulence, as varying storage, rather than uniform.
Changed the respective blocks as well.

Continued to clean the blocks, adding more meaningful names for inputs and outputs for the GUI. Moved dPdu and dPdv from Derivatives menu to the Inputs menu since they're global variables.