Added rsshell.py
Added rsshell.py

The plan is you're using your shell, then you run rsshell.py to load the
environment for the red spider project. What really happens is that
rsshell.py launches a subshell with the appropriate environment
variables set. The only odd thing from the user's perspective is that
when they want to quit, if they use "exit" or ^D or something, they need
to exit from two shells, not one. Oh, and command history might not work
right between inside and outside a call to rsshell.py

neil@milligan ~/m/t/src> env | grep RED_SPIDER
neil@milligan ~/m/t/src> ./rsshell.py
neil@milligan ~/m/t/src> env | grep RED_SPIDER
RED_SPIDER_ROOT=/home/neil/misc/the-red-spider-project
neil@milligan ~/m/t/src> exit

Goodbye
neil@milligan ~/m/t/src> env | grep RED_SPIDER
neil@milligan ~/m/t/src>

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