Remove hbase-examples from hbase-assembly

hbase-assembly is supposed to contain programming examples for HBase.
However, it is added to the assembly API, and becomes part of the HBase distrbutions.

On hand this adds some potentially useful components and coprocessors to HBase, on the other hand many of those are not production quality, and were never meant to be used as-is.

It also adds the Curator libraries to the general HBase classpath, which are used but by but a single example.

Removing hbase-examples from the assembly would fix both problems.