Implement GetWatchVar to replace expression interpreter

This is an internal method function in the LiveRunner that inspects the
value of any expression
Fix watch complex expressions

Added complex watch testcases
Copy debug information of an identifier to its SSA transformed node
Merge pull request #114 from junmendoza/StableBranch_VariableInspection

Complex expression inspection
Merge pull request #115 from ke-yu/StableBranchWithTestcases

Fix two array related defects (MAGN-619, MAGN-337)
Add test cases for LiveRunner