Version 4.5.2 (Important bug fix)

Through a stupid mistake of mine, a nasty bug was introduced into 4.5.1: a few vital bits of information were not written into non-volatile storage, and therefore not preserved through a power-off or re-boot. The information affected by the bug is the selected Koch lesson, and WiFi information. This has been fixed in this maintenance release. It might mean that you need to update from 4.5.1. by USB, unless you had a WiFi setup with a previous version!