word: store data entries as prepared subarrays

word: store data entries as prepared subarrays

Time to split strings is comparable to directly loading structured values.
Considered hashes for scalability with more (optional) columns, but not
worth the cost at this time.

Benchmark loading 1264 rows in perl:
	      	rate	memory	size
	strings	468/s	 52kB	15kB
	split 	257/s	152kB	 "
	arrays	221/s	133kB	17kB
	hashes	126/s	188kB	27kB