DictId handling by LexiconSet

[mh-northlander]

Currently dictionary id part of WordId is handled by several classes (LexiconSet, DoubleArrayLexicon, WordIdTable, ..).

DictId is for using multiple lexicons and LexiconSet should be responsible for modifying it.

[mh-northlander]

By removing dictId handling from lexicon interface, we can reuse lexicons in multiple LexiconSet i.e. multiple dictionaries.