Add icu-bidi package.

Change-Id: I2b32b84bfad5e2299db55296a52754bcda98b4a5
Refactor: `Formatter` class tracks paragraph/inline state.

We create a new class to buffer paragraphs and track the current
paragraph/inline/env state.  Then we can run the unicode bidi
algorithm on each paragraph when we emit it (this isn't completely
implemented yet).

Change-Id: Ic04cb626eee65ff302becfee93402e23c5440174