add seed_id and entitlements doc

doc/ReferenceManual.textile

@@ -450,6 +450,7 @@ The +rake config+ task will dump the project configuration. Each configuration v
 |+sdk_version+ | Version number of SDK to target, as a +String+. The default value is the version number of the most recent SDK in +platforms_dir+. Example: +'5.0'+|
 |+codesign_certificate+ | The name of the certificate to use for codesigning, as a +String+. The default value is the first iPhone Developer certificate found in keychain. Example: +'iPhone Developer: Darth Vader (A3LKZY369Q)'+.|
 |+provisioning_profile+ | Path to the provisioning profile to use for deployment, as a +String+. The default value is the first +.mobileprovision+ file found in +~/Library/MobileDevice/Provisioning+. |
+|+seed_id+ | The application provisioning identifier, as a +String+. It is a unique (within the App Store) 10 characters identifier generated by the provisioning portal. The default value is the first application identifier found in the +provisioning_profile+. |
 
 Custom values for the configuration settings can be added by tweaking the +Motion::App.setup+ block in the +Rakefile+ file.
 
@@ -529,6 +530,27 @@ Motion::Project::App.setup do |app|
 end
 </pre>
 
+h4. Entitlements
+
+Entitlements confer specific capabilities or security permissions to an application. You may be required by Apple to request an entitlement when trying to access a specific feature of the system.
+
+An application running on an iOS device that does not have the proper entitlement for a functionality will fail at runtime when trying to use such functionality. It will also not be accepted into the App Store.
+
+Entitlements are used during the code-signing part of the build process.
+
+The +entitlements+ method of the +Rakefile+ configuration object returns an empty +Hash+ object by default, that the developer can modify to set appropriate keys and values.
+
+For instance, our video player might require access to the keychain to store the user credentials. According to the documentation, the +keychain-access-groups+ entitlement must be requested, passing a combination of the application provisioning identifier and the application identifier, respectively exposed as +seed_id+ and +identifier+ in RubyMotion.
+
+<pre>
+Motion::Project::App.setup do |app|
+  # ...
+  app.entitlements['keychain-access-groups'] = [
+    app.seed_id + '.' + app.identifier
+  ]
+end
+</pre>
+
 h4. Advanced Info.plist Settings
 
 An iOS app has its configuration described into the +Info.plist+ file, which is located inside the application bundle. This file contains a set of keys and values. It is fully documented in the "Info.plist reference":http://developer.apple.com/library/ios/#documentation/General/Reference/InfoPlistKeyReference/Introduction/Introduction.html guide.
@@ -560,7 +582,7 @@ The following steps are performed:
 # It compiles each Ruby source code file into optimized machine code, translating the Ruby syntax tree into an intermediate representation language (using "LLVM":http://llvm.org/), then assembly. The compiler will generate code for either the Intel 32-bit (+i386+) or ARM (+armv6+, +armv7+) instruction sets and ABIs depending on the target.
 # It links the machine code with the RubyMotion runtime statically to form an executable. The linker also includes metadata for the C APIs that the project uses, as well as 3rd-party libraries vendored from the configuration.
 # It creates an +.app+ bundle and copies the executable there. The +Info.plist+ file is generated based on the project configuration. Each resource file in the +resources+ directory is copied in the bundle.
-# It codesigns the bundle based on the certificate and provisioning profile specified in the project configuration.
+# It codesigns the bundle based on the certificate, the provisioning profile and the entitlements specified in the project configuration.
 
 Normally the user does not need to explicitly build the project, as the +build+ task is a dependency of the other tasks.