add cancellation checks in continuations
add cancellation checks in continuations

npmurphy/MBrace.Core,palladin/MBrace.Core,krontogiannis/MBrace.Core,krontogiannis/MBrace.Core,dsyme/MBrace.Core,palladin/MBrace.Core,mbraceproject/MBrace.Core,mbraceproject/MBrace.Core,npmurphy/MBrace.Core,dsyme/MBrace.Core