Define MONO for DebugMono and ReleaseMono in the PalasoError project

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branch : FlexBridge2.0
Remove <RequiredTargetFramework>3.5</...> from all csproj files

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branch : FlexBridge2.0
Disable PalasoError from building for ReleaseMono

--HG--
branch : FlexBridge2.0
Tweak test for null data in AsyncProcessOutputReader

--HG--
branch : FlexBridge2.0