Installation / configuration doc enhancements

[skeller]

Took me a bit to figure out the following:

• Authentication of couchdb must work. Individual users are authenticated by couchdb (which also serves the webpages). imes.py -I (interactive mode) can be used to add users.
• The system-wide inotify per-user watcher limit needs to be increased for big media libraries as imes adds a watcher for each directory in the library. Otherwise the limit is reached after some runtime and imes quits with uncatched exception. The limit can be increased by putting a file in /etc/syconf.d/ with this:
  fs.inotify.max_user_watches=131072
  Or (temporary) by using sysctl -w inotify.max_user_watches=131072

Maybe those two points can be put into the readme.