ios: single xcode and cleaned configurations

Use just one xcode, namely the one of xcode-select (like qmake)
cleaned iosconfigurations:
 * cleaned now unneded xcode paths
 * using static methods, removed IosConfig

Change-Id: Icc4d1bc1063a5f65230736a47b4ca9b139fa79e0
Reviewed-by: hjk <hjk121@nokiamail.com>