Bump client minor version to avoid triggering crash

This is a sneaky workaround for #1606 (closed). Briar 1.1.7 doesn't consider that a contact supports image attachments unless the client minor version is exactly 1, so it won't take the code path that triggers the bug. Current master considers that a contact supports image attachments if the client minor version is greater than 0, so this branch and current master are still able to exchange images.

We should make a stable release that incorporates the (already merged) fix for #1606 (closed), and new alpha releases for 1.2 and 1.3 that incorporate this fix so they don't crash contacts running older stable releases.

Closes #1606 (closed)