Add UIDevice+ADJAdditions and NSString+ADJAdditions to static lib target

Those files missing from the static lib target, so it was crashing with the following exception for me:

`-[UIDevice adjMacAddress]: unrecognized selector sent to instance 0x1ed2bb70`

This happens when adding the Adjust Xcode project as a sub-project and linking libAdjust.  Likely happens when pre-building libAdjust.a and adding it and related header files to a project.