Add a build configuration for profiling

[speckdavid]

We would like to add a build configuration for profiling with pprof which is a tool for visualization and analysis of profiling data.

[speckdavid]

There are now 4 different build options: release, debug, release_profile and debug_profile. The debug mode has been changed from -O3 optimization to -O1 optimization.

When you run the planner in one of the profile options, profiles for the parser and search are created.

We should probably add an explanation to the wiki.

• Install gperftools and google-pprof:
  sudo apt-get install google-perftools libgoogle-perftools-dev google-pprof

• View a profile (change binary accordingly):
  ~/go/bin/pprof -web builds/release-profile/search/search prost_search.profile

• Note, that I had to install pprof with the following command.
  go get -u github.com/google/pprof