ratpac.sh exists in path

[MorganAskins]

By convention source looks in $PATH for a script when calling

    source ratpac.sh

This is intended for the command. Right now ratpac.sh lives in a place added to path by ratpac.sh so if a user tries to load a new version of ratpac (often the case) then if they do

source ratpac.sh

nothing will change, but if they do

source ./ratpac.sh

from within that new ratpac directory, they will correctly source the new version of rat-pac.

Possible solutions:

1. Educate everyone on correct usage of source.
2. Remove ratpac.sh from $PATH.

Note: geant4-config and thisroot.sh both live in $PATH as well so we are consistent with those programs already.