Remove unneeded string initializations (strcpy will initialize them).
catalogGUI: add mechanism for showing help on commands.
catalogGUI: add help for most commands and add some missing ones.
catalogGUI: add help text for more functions.
Port limit solving function from SMIB. Unfortunately doesn't solve a lot of limits, due to "divide by zero" errors, and gets some others wrong.
Change some functions to work better with infinity. At last, tan(pi/2) is no longer some huge float...
Forgot something from smib...
catalogGUI: add command reference for the remaining two commands.