Fixed enterprise event type filtering

Added serializable values for EnterpriseEventType so that
IEnterpriseManager.GetEnterpriseEvents can properly filter the event
stream.
Added GetEnterpriseEvent() overload w/out paging
Fixed enterprise event bug in RequestHelper
Fixing pagination; Issue #46
Merge branch 'master' of https://github.com/jhoerr/box-csharp-sdk-v2

Conflicts:
	BoxApi.V2/Model/Folder.cs