Move idsToWordVector and targetToVector from WindowModel to WordMap

[pmanion0]

The two functions idsToWordVector and targetToVector would fit better in WordMap (and get unit tests). They also have bad names.

Tasks:

• [ ] Move idsToWordVector to WordMap (and get a better name)
• [ ] Move targetToVector to WordMap (and get a better name)
• [ ] Add unit tests for both