utility: add str_list and str_list_inner helpers

These convert lists to string using str, instead of repr, for the member objects. The
_inner variant does not append the brackets, as this is widely used in operator shortStr function.
raco: implement proper repr, str project-wide

See #273. Note that `%r` is the repr version of `%s`, and that `!r` is
analogous for string.format.
myrial_test: test that plans are correct when translated through repr

@7andrew7 and better ideas? I don't love the blanket import-everything-ever at the top.
myrial_test: remove replace_with_repr to utility file

This at least encapsulates importing everything from the project
in its own file.
Merge branch 'master' into proper_repr

Conflicts:
	raco/expression/expression.py
Merge pull request #274 from uwescience/proper_repr

Proper repr