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

TACHYON-182 Add checkstyle to the maven build system so we could reduce time to do style check for contributions following Google style.
Fixed violations reported in the current master branch.

Note that currently you need to run
  mvn checkstyle:check or mvn checkstyle:checkstyle
to run the check.

You will see some warnings on public member for Tachyon configuration classes:
  CommonConf
  MasterConf
  WorkerConf
  UserConf
due to naming of their public member as all caps.

Once we stabilize the code we could hook it to build system to fail when checkstyle fail.
Yes, it is also preferable style for new Java program. Using parameter[] is
C style of array declaration which is not recommended.

On Saturday, October 18, 2014, Haoyuan Li <notifications@github.com> wrote:

> In core/src/main/java/tachyon/command/TFsShell.java:
>
> > @@ -35,7 +35,7 @@
> >     *
> >     * @param argv [] Array of arguments given by the user's input from the terminal
> >     */
> > -  public static void main(String argv[]) throws IOException {
> > +  public static void main(String[] argv) throws IOException {
>
> Is this part of the Google style? Using type[] parameter instead type
> parameter[]?
>
> @aarondav <https://github.com/aarondav>
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/amplab/tachyon/pull/473/files#r19057755>.
>