helper fn for rendering lsystems

iterates a char->char grammar n times, then renders it in
a turtle
do a different lsystem
add random_dispatcher function

for choosing functions with weighted probabilities. retrofit
it into Ifs.jl
make lsys symbols be ints rather than chars

avoids dict lookup every char. seems a bit faster.
rm cruft
eliminated explicit state for lsystems

they now run disgustingly fast and are somewhat more
elegant.