Bidi: Proper fix for mixing of RTL, LTR, number and puncation marks.

This fixes the following case, in which the previous behaviour was not satisfatory:
- Writting combinations of RTL text and punctuation marks. i.e typing "RTL 123 (456)" previously did not render correctly.
- The above also happened in most case where apps render the text. Striking examples are twitter (for example cases with numbers in parentheses in RTL text) and gallery apps where the number of pictures is appended at the end of the folder name (i.e. try a RTL folder name with a number at the end of its name in quickpic).
- Gmail app - fixed serious problems both with RTL sender names (any case where there is both an RTL sender name and a LTR one) and with subject lines containing combinations of RTL and LTR/numbers/puncation marks (for example subject "RTL (123)").

Also cleaned up a bit the logic and code of StaticLayout.java.

Change-Id: Iad6cbd21592ca70878d95134cb87b1d16bc365fa