gluon-luci-theme: new theme, still magenta/yellow

This is the initial version of our new configmode theme. It's far from
finished but at least configmode looks good. There are lots of
declarations copied from OpenWRT's default theme so most other luci
modules would be somewhat usable when shown using this theme.
gluon-config-mode,luci-admin: use gluon-luci-theme

This makes gluon-config-mode and gluon-luci-admin depend on
gluon-luci-theme instead of luci-theme-openwrt.
gluon-config-mode: replace inline style with class

Replace the inline stylesheet for the public key box on the reboot page
with a CSS class so it can be styled using the theme.
gluon-config-mode: remove subsection headings

Those headings do not convey much information make the wizard less
compact. The help texts will be rewritten to guide the user instead.
Merge pull request #10 from freifunk-gluon/luci-theme

add new luci-theme