Display reject percentage instead of absolute accepted/rejected values

Changed GPU status line from "A:xxxxx R:xxx" to "R:0.0%". It shows (rejected/(accepted+rejected))*100, which is the percentage of rejections for a GPU. Total accepted and rejected in top status is unchanged.

GPU status lines now show both threads and intensity.
core: Revert printing threads for every GPU, this setting is not modifiable at run-time.
Code cleanup after last commit.

Display reject percentage in a fixed-width field.