Maintain dict scores in model by arrays instead of tuples

[vbkaisetsu]

This branch maintains dictionary scores in the model by arrays instead of tuples.

Currently, dictionary scores are maintained by tuples of three scores (left, inside, right), so users cannot specify inside scores individually.
It means that users cannot specify scores depending on the context.
For example, the current framework cannot specify scores of 外国人参政権 directly.

By this change, users can specify scores individually as follows:

外国人参政権,10000 -10000 10000 10000 -10000 10000 10000,外国/人/参政/権

[kampersanda]

LGTM