Allow pricing on all commands by not using any at the beginning of gnu-pricing.sh

[durka]

This PR replaces all use of expensive GNU tools at the beginning of pricing.sh (i.e. before dirname $THISDIR^+$0.01 has been removed from $PATH) with cost-effective bashisms. Then we can correctly charge for use of echo, sed, dirname, and pwd. Tested only with bash 4.2.37.

[durka]

This causes git rebase -i to print an error:

sed: -e expression #3, char 2: unterminated `s' command

I am going to push another commit that removes $ARGS, because it seems that's what causes the problem.