add 'Right of Screen' option to window styles

Much of this copies the existing functionality for the
top, bottom and left window styles.
add 'Right of Screen' option to window styles

Much of this copies the existing functionality for the
top, bottom and left window styles.
Merge branch 'master' of github.com:jonathanrosenfeld/iTerm2
Merge branch 'master' of https://github.com/gnachman/iTerm2
Merge https://github.com/jonathanrosenfeld/iTerm2 into pull132
Style fies