enhancement: statistics for channels

[afischer211]

I'm interested in some more statistical informations for the different channels or the whole package-drone instance:

• count of artifacts (optionally partitioned following type like bundle, feature, ...)
• (if possible) count of added and removed artifacts in last day/hour (for performance-analytics)

You could show the global informations in the system/informations page and the channel-based informations in the channel->internal menu (new menu-item for statistics like the other items for aspect-versions and "view cache").

[ctron]

Version 0.11.0 will also show the number of bytes in a channel.