Refactor remoteconfig HTTP content files

Reorganise lib-remoteconfig/http/content web assets: remove many legacy headerized JS/HTML fragments, add consolidated/modern pages and scripts (dmx, rdm, rtc, showfile, time, static, modern/config_ltc), and update includes, index, styles and pixeltype resources. Also update content.h, date.js.h and regenerate logic (generate_content.cpp made executable) so the new set of embedded content is produced.

Author: vanvught