#CAROLINE-41/1: Raw version of performance measurement is implemented via Clock and TimeLog classes. Examples of usage are in caroline.cc Also some minor style fixes are made to satisfy linter.
#CAROLINE-41/1: Logging of current time from Clock into TimeLog is moved to destructor.
#CAROLINE-41/1: Log is written to LOG(INFO). TimeLog changed to singleton. Time is measured in us. Some testing and documentation added. Writing to LOG(INFO) is not tested. Calls in caroline.cc are still Clock('name').
#CAROLINE-41/1: Namws of performance clocks are now in time_performance_field_names.h
#CAROLINE-41/1: 1000000 is made a constant in time_utils.cc
#CAROLINE-41/1: rebase made.
Merge pull request #125 from it-workshop/wp/CAROLINE-41/1

#CAROLINE-41