Release-0.7.0

This release introduces a final round of deprecations in this new version release, as well as introducing some brand new diagnostic features.

• #597 adds some better tutorials for AutoFilter
• #596 removes CoreContext::Snoop and CoreContext::Unsnoop
• #585 adds BasicThread::IsMainThread
• #594 and #592 add a feature designed to make it easier to debug filter graphs. You can now dump graph topologies to a DOT file and then render them to an svg with graphviz
• #588 and #581 allow you to display the context topology
• #575 adds some simple methods that let you diagnose AutoFilter issues
• #593 adds the basic_timer function for timer purposes
• #584 clears thread pool limits on the thread pools introduced in v0.6.0
• #579 allows multi-in filters to declare shared pointer inputs
• #577 prevents the global context from being restored as the current context in cases where no context was previously current
• #576 eliminates the ContextCreator type (finally!)
• #572 adds AutoPacketFactory::CurrentPacket