Added NullSafeAccessor - the way to safely access properties of nested beans.
This solution is a competitor to SafeChain (https://github.com/alexradzin/SafeChain).

On the way limited depth when discovering the source root. Otherwise this mechanism might cause problems
if file being searched is not found in reasonable location. This mechanism should be fixed to be more stable.
Merge branch 'master' of https://github.com/alexradzin/BeanCrumbs