Add simple macros for the 4 session-benchmarking methods

Signed-off-by: Nano <a>
Allow for nested session benchmarking by passing session object to Benchmark Target

Signed-off-by: Nano <a>
Add optional __STEP__ parameter to MGBenchStep which lets you override the default Class/Method helper string

Signed-off-by: Nano <a>
Rewrite custom macros to fix bug with optional __STEP__

Signed-off-by: Nano <a>
Remove redefined macro errors in MGBenchmark.h
Remove redefined macro errors in MGBenchmarkSession.h
Merge pull request #9 from workwithnano/master

Add simple macros for the 4 session-benchmarking methods