Replace .py2store_configs with {app_data_folder}/py2store

[thorwhalen]

This issue addresses the concern of where to put app/package data.
It resulted in the proposal of the
get_app_data_folder
function.

We should use this function to replace the ~/.py2store_configs with {app_data_folder}/py2store.

We need to figure out a good transition protocol too. For example, if the old folder exists, use that, but issue a warning telling the user they can move it to the new place to stop the warnings. Also let them know that the current package will then function as usual, but if they have anything else that depends on the old location, they should refactor there too.