More consistent naming with screen size variables using xs, sm, md, and lg

BS3 commit 61caed21e2553e1be29d98bd83c8e6ac06565ecd
add role=menu to html

BS3 commit 1d53dd31f5a6c9be04177e251756909847e6fc0a
add the customizer builder to the default grunt task

BS3 commit 5d84e02c1caf6c670dea2a877b4a375615871341
Add alert for customizer errors

BS3 commit 90d5e48f5f2d9d9619eb819fc914804064a3adaa
improve pagination's active state so it looks less like the active state and more like active nav items. fixes #9634: turn off overflow-y when the navbar is re-expanded into horizontal mode. fixes #9622: reset to inline-block for img-thumbnail, but keep block for .thumbnail > img. fixes 9629. fixes 9647: ensure open dropdown toggles get .active styles. nuke bg image on active/open for buttons for when we add gradients. fixes 9655: scrope list group styles in panels to immediate children only. Fixes 9663: Add offset overrides for medium and large grid tiers. fixes 9663: second part, reset pushes and pulls in md and lg grid tiers. xs button is xs-er (fixes 9695). fixes 9642: open dropdown nav items get proper styling. switch to margin on navbar-nav to avoid stacking negative space reported. Justified nav now responsive; example updated accordingly (fixes 9708). fixes 9475. Make negative margins on rows the default, not just in containers, and add padding to body to compensate. fixes #9436 more: put padding on containers, not the body because full width elements. Fixes 9552: Downsize and use whole numbers for panel title to prevent odd 1px bug. fixes 9538: prevent Firefox rendering bug via some border-fu. 2px border on thead th elements for just a tad more separation. Fixes #9752: clear floats in .panel-body

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