Add ApiOption overloads to methods on IIssuesClient

[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 IIssuesClient with a new parameter ApiOptions
• Implement the new method on the class which implements IIssuesClient
• Add an overload for this method on IObservableIssuesClient with a new parameter ApiOptions
• Implement the new method on the class which implements IObservableIssuesClient

This needs to be done for each of these methods:

• Task<IReadOnlyList<Issue>> GetAllForCurrent()
• Task<IReadOnlyList<Issue>> GetAllForCurrent(IssueRequest request)
• Task<IReadOnlyList<Issue>> GetAllForOrganization(String organization)
• Task<IReadOnlyList<Issue>> GetAllForOrganization(String organization, IssueRequest request)
• Task<IReadOnlyList<Issue>> GetAllForOwnedAndMemberRepositories()
• Task<IReadOnlyList<Issue>> GetAllForOwnedAndMemberRepositories(IssueRequest request)
• Task<IReadOnlyList<Issue>> GetAllForRepository(String owner, String name)
• Task<IReadOnlyList<Issue>> GetAllForRepository(String owner, String name, RepositoryIssueRequest request)