Update for build config whitelisting

Required before https://github.com/CocoaPods/CocoaPods/pull/1668 .

Intended:
* Removes Pods.xcconfig, adds Pods.{config}.xcconfig
* Links with pods using OTHER_LDFLAGS instead of product reference

Weird:
* Random reorganization of xcodeproj properties -- I blame Xcode.
* /usr/local/bin/git => /usr/bin/git, dunno why
* Also adds "ALWAYS_SEARCH_USER_PATHS=YES", dunno where that comes from
* Adds PODS_* build settings, dunno where those come from