Add closing a session with cmd-w as an interaction that turns off the 'don't quit when the last window is closed' safety valve

In issue 999, a problem was raised that iTerm2 won't quit when the last window is closed if it's been running for less than 10 seconds. The 10-second safety valve was added to allow you to fix a busted profile which could cause the last window to close immediately when the app starts. The problem is that you might want a short session. This change disables the safety valve if you type in a session or intentionally close the window.

Only ask about saving prefs to custom folder when feature is enabled and no folder is already specifie

Add gesture recognizer for three finger taps to act like three finger clicks, gated by ThreeFingerTapEmulatesThreeFingerClick pref

If the tmux profile specifies a nonpostive value for rows or columns, use 1 instead to prevent an assertion

Render private-use range unicode chars (except the four reserved by iterm). Some fonts use them for fancy special characters and it's nice to support that. The down side is that for normal fonts they'll render a bit uglier as a double-width character, but you shouldn't get them often anyway

Reset focus mode with RIS

Fix crashing bug when printing binary files. Not sure of the exact cause, but the code is much cleaner and full of asserts now.

Fix bug where partial csi ! codes caused a bogus memory reference; streamOffset became a huge number

Fix up some bugs in OSC 52 (clipboard integration) - the preference panel change somehow went missing. Also, when stripping control codes, also reduce the overall length of the string to copy