UpdateManager configuration

- Implemented UpdateManagerConfiguration class to store the
configuration data specific to UpdateManager
- This class can be serialized and de-serialized into/from xml file.
- UpdateManager initializes the configuration from
UpdateManagerConfig.xml file if present in Dynamo installation,
otherwise by default it will point to production servers for
UpdateFileLocations and Signature file location.
- In Debug build it creates UpdateManagerConfig.xml file if not present
and saves the default configuration data. The same file can be used to
redirect the update location to the dev S3-bucket from a release build.
Addressing review comments
created CustomNodeIcon on StartPage
Change as feedback
Adding testcase for UpdateManagerConfiguration
Rename GCAnonymousSymbols() to GCSymbols() and some cleanup
Remove callsite gc root
Update test cases for verifying reference count
Using RuntimeMemory.PushFrameForGlobals() to extend stack for global variables
Handle the case that expected value is null
GC deactivated symbols
Fix test cases
Implemented temporary storage for custom node GraphSyncData
Fix test cases
Updated CustomNodeDefinition.Compile to remove scheduler related code
Reimplemented CompileCustomNodeAsyncTask to work with GraphSyncData
Implemented EngineController.ProcessPendingCustomNodeSyncData method
Not use freelist in verification mode
Updated DynamoModel to call ProcessPendingCustomNodeSyncData
Resurrected scheduler