Small bug fixes

This release is very small. It fixes up two bugs:

1. The deprecation of a function for fetching user fields. We are now using core_user\fields::get_picture_fields
2. Trades not showing properly due to the stdClass not being defined.

I have been playing around with other enhancements to block_stash, but I'll only post details for them when they are finished.
Thank you for your support and I hope that you continue to enjoy stash with Moodle.