Release of 0.99.3

Version 0.99.3 has just been released. It fixes an annoying bug introduced in 0.99.2 which prevented slider labels to be visible. Additionally, the documentation has been considerably extended in this release, see Another notable improvement is the unified treatment of points, texts and images. It is not completely done, but at least the main construction methods are identical now.

Many thanks to all of you who reported errors and helped to fix them!