Add command and variable descriptions

src/Makefile.d/versions.mk

src/command.c

src/command.h

src/console.c

src/d_main.c

src/dedicated/i_video.c

src/filesrch.c

src/g_demo.c

src/g_game.c

src/g_input.c

src/hardware/hw_main.c

src/hu_stuff.c

src/i_time.c

src/lua_consolelib.c

src/m_anigif.c

src/m_cheat.c

src/m_menu.c

src/m_misc.c

src/netcode/d_clisrv.c

src/netcode/d_netcmd.c