RSS: Make the cache bigger in order to prevent duplicated announces.
RSS: Fix support of feeds that do no have guid fields. Closes GH845.
Owner: Make error message of plugin loading at startup more explicit. Closes GH-850.
PluginDownloader: Sort `repolist` output alphabetically
Merge pull request #856 from nyuszika7h/plugindownloader-sort

PluginDownloader: Sort `repolist` output alphabetically
Aka: Add `set` command to change existing aliases