Bunch of fixes in LookupTable FSM

Hi Graham-sensei,

These are the fixes I made for lookuptable FSM.
Basically, I removed the "default_symbol" config as it doesn't make sense for multi head symbol. 

The only one problem is: seems that glue-rule for hiero with annotated non terminal is still intractable with the current architecture. (we have to list all combinations of tuples of (span, head_symbols)?)

Philip