Bug 1035536 - move CSS to themes directory, r=dao

--HG--
rename : browser/base/content/aboutneterror/netError.xhtml => browser/base/content/aboutNetError.xhtml
rename : browser/base/content/aboutneterror/info.svg => browser/themes/shared/aboutNetError_info.svg
extra : rebase_source : c78b55b877ded23ad05aa942ab7983516a688cd8