subnav for icons section

BS3 commit 7a7971d
update reference to value of base line-height

BS3 commit a19fda6
Unitless line-height

BS3 commit 6fba68e
More forms overhaul

BS3  commit 293a3ba
Fix up navbar forms by using inline form as a mixin; fix docs for those

BS3 commit 7b6352d