add static library project for IASK

* add static library project
  provide proper build settings, formatting, unit tests
* add workspace to repository (combines app + static lib project)
* modify sources to work with static lib project
  the sample project uses recursive-header search paths to find
  IASK headers in the different subfolder (Controllers/.. Models/,…).
  The static lib sample app uses the installed headers which are installed
  in InAppSettingsKit/ subfolder
* prepare unit tests for IASK which will live in the static library project
* static lib project configuration is done in xcconfig files for easier maintenance
allow initialization with a custom NSUserDefaults instance

or something that looks like one. This will allow easier testing
as well as custom NSUserDefaults implementation, subclasses,...
test abstract store
test IASKSettingsStoreFile
fix formatting
add "Store" group in xcodeproject
remove unused define
add initial test for IASKSettingsReader

* refactor IASKSettingsReader's initialzer to allow reading from bundles
beside the application's main bundle
* add the Settings.bundle from sample app
fix formatting
cleanup

remove unneeded declarations
cleanup

* use auto-synthesized properties
* move ivars to class extension
add reader test which locates settings bundle
add test to find plist besides Root
more reader tests

* simple parsing
* hide/unhide keys
test hiding complete group/section
test device-dependent plist
test platform suffix creation

* refactor method to take interface idiom as parameter
(there's no need to check the platform version, UIKit macro does that for us)
cleanup

* move internal-only strings to .m
* also, use NSStrings instead of defines for type safety
* remove kIASKBundleFileName, as it wasn't used
* unify naming (non-capital k)
adjust formatting
cleanup

* use new array initializers
* make variable names more explicit