Update PBXFileSystemSynchronizedGroupBuildPhaseMembershipExceptionSet to support PBXResourcesBuildPhase

[triplef]

When adding a bundle (such as an .mlpackage) inside an Xcode folder to a target, the "Copy Resources" phase will have an exception like this:

86522D262ED065A3005F54C6 /* Exceptions for "MyFolder" folder in "Copy Bundle Resources" phase from "MyApp" target */ = {
	isa = PBXFileSystemSynchronizedGroupBuildPhaseMembershipExceptionSet;
	buildPhase = 7AA69A92145AF32700190537 /* Resources */;
	membershipExceptions = (
		MyModel.mlpackage,
	);
};

When attempting to read this project an error would occur:

[Xcodeproj] Type checking error: got `PBXResourcesBuildPhase` for attribute: Attribute `buildPhase` (type: `to_one`, classes: `["PBXSourcesBuildPhase", "PBXCopyFilesBuildPhase"]`, owner class: `PBXFileSystemSynchronizedGroupBuildPhaseMembershipExceptionSet`) - 7AA69A92145AF32700190537 <Nanaimo::Dictionary {"isa"=>"PBXResourcesBuildPhase", "buildActionMask"=>"2147483647", "runOnlyForDeploymentPostprocessing"=>"0", "files"=>[]}>

Note that a PBXResourcesBuildPhase doesn't have a name, so I had to adjust the display_name method accordingly.

See also #986.

[egec1]

What are we waiting to merge this?

[xavierserrai]

Dears,

Is this project currently maintained or will this be discontinued as the whole cocoapods repository?

Thanks,

@endocrimes