Support for latest Spark version in oozie workflow xml

[sushrutikhar]

inorder to specify the latest version of spark in oozie action specify as:
<version>0</version>

[pallavi-rao]

@sushrutikhar As discussed, we shouldn't be doing multiple Launchers, unless the client API's backward compatibility is severely broken by Spark.

We should de-couple the Launcher from sharelib and allow users to choose the sharelib that needs to be loaded at runtime. This way, movement across minor releases will be easy and all the Oozie admin needs to do is just add a new sharelib and update the sharelibs (no Oozie release required). Also, the users will be free to move to the version of their choice at their pace.

Please make changes along these lines.