Make RetryPolicy configurable

[rintcius]

Outcome Desired

Make it possible to configure the RetryPolicy - see http://docs.datastax.com/en/drivers/java/2.1/com/datastax/driver/core/Cluster.Builder.html#withRetryPolicy-com.datastax.driver.core.policies.RetryPolicy-

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Definition of Done

It is possible to specify a RetryPolicy that will be used for the migrations. When no RetryPolicy is specified the default is used.

[hhandoko]

Hi @rintcius , I can have a look at adding this in the next release (April - May).