<admin stats> refactor and mods for admin console

Results subclasses were all moved out to a lib file.
Admin::Stats became Admin::Stats::Maker in order to have clean
separation of namespaces and make Rails autoloading happy.
Miscellaneous bits added and adjusted.
<admin suggestions> library to suggest admin changes

Generates config-driven suggestions for:
* Adding capacity
* Removing capacity
* Taking note of unresponsive nodes
* Fixing suggestion config values
Extensible with subclasses.
<admin console> capacity planning

https://trello.com/c/nqlnXBRQ/58-5-allow-admins-to-do-simple-capacity-planning-from-the-admin-console-admin

The admin console displays important systems statistics for capacity
monitoring and planning in a nice visual format. Suggestions can be
configured to display for common needs such as adding capacity.
Various other tweaks and improvements have been made.
Bug 1004160 - admin console stats graphs fail to load with arg error
<admin suggestions> fix bug 1004157

https://bugzilla.redhat.com/show_bug.cgi?id=1004157
Admin console suggestions suggest adding nodes to district NONE which is
impossible
<admin suggestions> fix bug 1004297

https://bugzilla.redhat.com/show_bug.cgi?id=1004297
unexpected type Capacity::Add::District in admin console

When suggesting the addition of a district, that suggestion accidentally
overwrote the wrapper suggestion; since it's a subclass, the difference
was not noticed immediately.
<admin suggestions> allow 1-node districts

Previously districts always got at least 2 nodes (else why have them?)
however in the case where gears are just used for compartmentalized
storage and almost all are idle, it can make sense to have just one node
in a district. The district then doesn't serve much purpose, but you'll
need it if you have set districts to be required for the installation.
It's sort of an odd use case but it is allowed.
<admin console> lower default active% to 5
<admin-console> tweaks to views

_head partial moved into namespace
favicon and loader-dark assets added
remove unneeded tracking in layout
<broker> compile assets in all envs
<admin console> edge case on suggestion display

On the main page, with 4 or fewer suggestions, they are to be inlined
with the profiles being displayed. However they weren't being displayed
at all if there was only one profile, as they were tied to the second
profile. Now they are tied to the first profile.
<admin suggestions> fix bug 1004671

https://bugzilla.redhat.com/show_bug.cgi?id=1004671
The count of nodes left is incorrect for suggestions when we have
multiple districts

The total nodes that could be created in all existing districts was
given, rather than how many could be created in a particular district.
Should correctly show per-district space for nodes now.
<capacity planning> review comments