UI: Add support for OBS_PLUGINS*_PATH env variables

Allow to load obs plugins from arbitary directory, specified by
OBS_PLUGINS_PATH and OBS_PLUGINS_DATA_PATH environment variables.
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f