Add a config that allows us to configure region-level storage policies

<property>
<name>hbase.hregion.block.storage.policy</name>
<value>HOT|ALL_SSD|...</value>
</property>
With this config, we can set region-level storage policies.

We have this config about CF storage policy:

 <property>
    <name>hbase.hstore.block.storage.policy</name>
    <value>ALL_SSD</value>
  </property>

But in addition to CF, we also have some other path under region path, such like .splits, 

recovered.edits, .tmp .

So i want to add a region-level config which could cover the whole path, and if you have any other requirements for the cf directory, you can continue to use the previous hbase.hstore.block.storage.policy to specify them separately.