decoder/timeline: improve decoding of still images

Merge pull request olive-editor#1116 from eszlari/patch-9

0.1.x / cmake: add ts/olive_uk.ts

Merge branch '0.1.x' of https://github.com/olive-editor/olive into 0.1.x

Merge pull request olive-editor#759 from eszlari/cmake-doxy

cmake: add doxygen

changed month version

removed unnecessary qimage from texteffect