Add ApiOption overloads to methods on IRepositoryPagesClient

[shiftkey]

As part of completing #760 a number of overloads need to be added to the client interfaces.

As an example, this has been added to IReleasesClientand IObservableReleasesClient.

The checklist for porting each method is:

• Add an overload for this method on IRepositoryPagesClient with a new parameter ApiOptions
• Implement the new method on the class which implements IRepositoryPagesClient
• Add an overload for this method on IObservableRepositoryPagesClient with a new parameter ApiOptions
• Implement the new method on the class which implements IObservableRepositoryPagesClient

This needs to be done for each of these methods:

• Task<IReadOnlyList<PagesBuild>> GetAll(String owner, String repositoryName)