add function to detect advanced stepping commands
support advanced stepping commands when the are available
Merge branch 'feature/no-srcref-debugging' into feature/advanced-stepping

Conflicts:
	src/cpp/session/modules/SessionBreakpoints.R
	src/cpp/session/modules/SessionBreakpoints.cpp
	src/cpp/session/modules/SessionBreakpoints.hpp
	src/gwt/src/org/rstudio/studio/client/workbench/model/SessionInfo.java
don't show step into / finish loop commands at the top level
Merge branch 'feature/advanced-stepping'