move ets:delete out of parse fun for benoitc/econfig#6
make set_value to empty the same as delete_value for benoitc/econfig#6
add inorder to modify multifile tests for benoitc/econfig#6
added a couple more subscribe tests for benoitc/econfig#6
Merge pull request #7 from unix1/fix-setvalue

Fix set_value to empty to behave like delete_value