Fixed mainmenu lua errors because of changes in get_textlist_index

Fixed lua error when none of the worlds or servers selected are and connect,
delete or configure buttons used.
Schematic: Read slice probability table from schematic descriptors
LuaVoxelManip: Add get_param2_data and set_param2_data
Update lua_api.txt documentation
Fix minetest.rotate_and_place() calling on_rightclick() with nil/random param for node