graphics/goxel: modernize the port and update to version 0.11.0

• Lowercase all but the first word of the COMMENT, adjust LICENSE to match the source code headers
• Drop unused dependency and INSTALLS_ICONS knob, massage USES and USE_GNOME lists as needed
• Install more complete set of high-color icons, do not capitalize loop iterator variable
• Provide more elaborate port description, move WWW line where it belongs these days (in the Makefile) and chase redirection
• Assume maintainership since previous maintainer had stepped down