reduce size of topbar and links in it

[#46399255]

** Reducing size of additional containers which hold
Share and About links is necessary also ...
credits icon: a bit smaller, more left padding

[#46425081]
layout cleaned up, experiment time displayed

Layout changed to move variable (temp) and output (experiment time)
close together. Model now only displays experiment time when model is
running.
minor edit - 1 decimal point for output
Merge branch 'wip_diffusion' of github.com:concord-consortium/lab into wip_diffusion