simplifies entry point and allows for command line execution

Replaced the `switch` logic in favor of a simple hash lookup table.

Gives actobotics_ChannelGenerator.rb executable permissions and
shebang (#!) interpreter for command line execution via:

    ./actobotics_ChannelGenerator.rb

There were also a few menu variables that had been redefined, i pulled out the
few that were being overwritten.

p.s. indentation/white-space ocd got the better of me.