build: introduce luci-base Merges libs/core, libs/ipkg, libs/web, libs/sys, libs/sgi-cgi, libs/sgi-uhttpd, modules/admin-core, themes/base and protcols/core into modules/base and renames luci-lib-core to luci-base.
libs/web: Allow to disable buttons in cbi models from the controller
libs/web: remove license comments from cbi templates, saves around 50% of their size
libs/web: add "back to overview" button to page actions if .redirect is set on the corresponding map
libs: merge libs/cbi into libs/web