Refactor corpura management

[hcoona]

We have at least 2 corpura:

• OALD extracted data.
• COCA word frequency list.

OALD

It provide 2 important components:

1. wordlists
2. meanings for a word.

COCA

It provide 2 important components:

1. wordlists
2. frequency ranks

Summary

So basically we need the following abstractions:

1. IDictionaryProvider to provide the word to meanings mappings.
2. IRankProvider to provide the word to frequency rank mappings.
3. IWordListProvider to provide the word list to filter words from the dictionary.