Add SyncFolderItems operation
Add SyncFolderItems operation

Returns a sync_folder_items_result containing all
relevant information.

bkircher/ews-cpp,otris/ews-cpp,bkircher/ews-cpp,bkircher/ews-cpp,m-Schlitzer/ews-cpp,m-Schlitzer/ews-cpp,m-Schlitzer/ews-cpp,otris/ews-cpp,otris/ews-cpp,otris/ews-cpp