Implement the multiple-starters feature:

- implement automata merging and concatenation
- change the command line parsing to allow multiple queries
- update the output format to denote which query a result set belongs to
- implement full evaluation of automata (associate each selecting state
with its result set)

Given queries Q1 ... QN on the command line, we can now:
- compute Q1, then Q2, ... , then QN on the same document, sequentially
- build one automaton that computes Q1, ..., QN in parallel
- compute QN(... Q2(Q1(root))) sequentially (materializing intermediate
results)
- build one automaton that computes QN(...(Q2(Q1(root)))) in one run.