TACHYON-193 TACHYON-194 First drop of Tachyon neo configuration

The PR includes:
-) TACHYON-193
Add new Tachyon properties file configuration to support file based configuration.

Add new code to support Tachyon properties configuration for runtime. 
This will be file based could be overriden via site specific configuration file or override collection in the TachyonConf class.
-) TACHYON-194
Add TachyonConf class to unify all Tachyon configurations.
Use single class TachyonConf to manage the configurations properties as key-value store.
The constants file is just to save the name of the properties itself.

I need to remove some unused strings constants later.

On Monday, November 24, 2014, bradley childs <notifications@github.com>
wrote:

> In core/src/main/java/tachyon/Constants.java:
>
> > @@ -49,4 +49,96 @@
> >     * Version 3 [0.6.0] Add lastModificationTimeMs to inode.
> >     */
> >    public static final int JOURNAL_VERSION = 2;
> > +
> > +  // Configurations properties constants.
> > +  // Please check and update Configuration-Settings.md file when you change or add Tachyon
> > +  // configuration properties.
> > +
> > +  public static final String DEFAULT_HADOOP_UFS_PREFIX = "hdfs:,s3:,s3n:,glusterfs:";
>
> Why do we have a file of static global constants still? Wasn't that one of
> the goals of the refactor?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/amplab/tachyon/pull/534/files#r20802904>.
>