Add checkstyle support for Google code style.

Add checktyle 2.8 to the maven checkstyle plugin to be able to corretly parse Google Java style rules.

First drop to fix code based on Google style.

Fix unit tests fail.
Fix rules on imports.
Remove commneted out rules.
Add checkstyle for Google Java style of constants name.
Add rule for StaticVariableName to check for static, non-final fields.
Merge pull request #473 from hsaputra/checkstyle_goog

TACHYON-182 Add checkstyle to the maven build system so we could reduce time to do style check for contributions