Cluster_info additions and fixes

This branch merges three other feature branches which, in total, add the following stuff:

* Add primitive flow control to the client -> server reporting protocol
* Add 'Suspicious link and monitor counts' report
* Display the `erlang:memory()` data both as-is and sorted with the biggest at the top (for lazy report readers)
* Add ability to specify which callback modules you wish to report on.
   The default is all available callback modules.
* Very basic HTML output, including table-of-contents-style links at the node & reports-per-node levels.