Improve send input to all sessions to support toggling individual sessions or senidng to just panes in current tab.

Improve font size estimator's estimates by erring on the high side of baselines. Consider normal low-hanging chars one at a time instead of all at once. Add performance optimizations (takes about 20ms on my Air).

Fix color of tabbar in fullscreen. Fix bug where fullscreen tabbar would go away when you cmd-tab and come back