TACHYON-8 [WIP] First drop of Tachyon neo configuration

The PR includes:
-) TACHYON-193
Add new Tachyon properties file 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.

Rather not reinvent this feature since it's not core to tachyon
On Nov 14, 2014 6:21 PM, "Henry Saputra" <notifications@github.com> wrote:

> In core/src/main/java/tachyon/conf/TachyonConf.java:
>
> > + * Configuration for Tachyon. Used to set various Tachyon parameters as key-value pairs.
> > + *
> > + * This class will contains all the runtime configuration properties.
> > + *
> > + * Clients of this class can create a TachyonConf object with <code>new TachyonConf()`</code>,
> > + * which will load values from any Java system properties set as well.
> > + *
> > + * The class only support creation using `new TachyonConf(properties)` which will override default
> > + * values.
> > + */
> > +public class TachyonConf implements Serializable {
> > +  public static final String DEFAULT_PROPERTIES = "tachyon-default.properties";
> > +  public static final String SITE_PROPERTIES = "tachyon-site.properties";
> > +
> > +  // Regex to find ${key} for variable substitution
> > +  public static final String REGEX_STRING = "(\\$\\{([^{}]*)\\})";
>
> It is another dependency which was ask not to do if possible (otherwise I
> already use Typesafe config).
> I added note to look at commons StrSubstitutor class later.
>
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> <https://github.com/amplab/tachyon/pull/529/files#r20398866>.
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