* Reduce the size of Terminal::Cell.
* Change colors and attributes in Terminal::Rendition to bitfields/bitmask.
* Change Cells to use UTF-8 strings instead of vector<wchar_t>. Store Rows in a vector instead of a deque.
* Add various Framebuffer::append() methods for more efficient passing of single and repeated characters.
* Change title/icon strings from deques to a vector typedef-- this is more for tidiness than any real performance.
John Hood