SPARK-1297 Upgrade HBase dependency to 0.98

Two profiles are added to examples/pom.xml :
hbase-hadoop1 (default)
hbase-hadoop2

I verified that compilation passes with either profile active.
There's already an `hbase.version` in the parent. This would need to be removed anyway. So why not just use it? it's possible people already use this to override the version in their own build.