first-run: Setup .bashrc as part of initial setup.

• Adds a kdesrc-run alias to ~/.bashrc, which takes care of sourcing the

prefix and starting the application that is given as argument.

• Ensures kdesrc-build itself is on the PATH

See issue #2 (I would close but I think there's more to do before we
consider ourselves done with all first-run setup in .bashrc)

Thanks to Felipe Peter for his first-time contribution to kdesrc-build! See MR !17