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.
I think this one is commented out from checkstyle github.
The rules are configurable and we could fine tune it once it is in.
The PR tries to cover as much as possible of Google style.

On Saturday, October 18, 2014, Haoyuan Li <notifications@github.com> wrote:

> In core/src/main/resources/tachyon_checks.xml:
>
> > +      <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
> > +      <message key="name.invalidPattern"
> > +               value="Method type name ''{0}'' must match pattern ''{1}''."/>
> > +    </module>
> > +    <module name="NoFinalizer"/>
> > +    <module name="GenericWhitespace">
> > +      <message key="ws.followed"
> > +               value="GenericWhitespace ''{0}'' is followed by whitespace."/>
> > +      <message key="ws.preceded"
> > +               value="GenericWhitespace ''{0}'' is preceded with whitespace."/>
> > +      <message key="ws.illegalFollow"
> > +               value="GenericWhitespace ''{0}'' should followed by whitespace."/>
> > +      <message key="ws.notPreceded"
> > +               value="GenericWhitespace ''{0}'' is not preceded with whitespace."/>
> > +    </module>
> > +    <!--         <module name="Indentation"> -->
>
> Why comment out these?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/amplab/tachyon/pull/473/files#r19057033>.
>