add PerfResultType to the summary report

- Each test should tell if the result is better with higher score or lower score.
- Without this, backend needs to remember which way is better for each test.
- This information should be displayed in visualization / table as well so
  that users do not need to remember which way is better.

Change-Id: I1ae5308d609887b2e0cc9a59c00667f892e29adb
12 files changed