Build and coprocessor support for Apache HBase 0.98

Add build and coprocessor support for Apache HBase 0.98.

Apache HBase 0.98.4-hadoop2 will be released this evening and Maven artifacts will propagate within 24 hours. Until then to test the changes please substitute the version '0.98.3-hadoop2'.

In 0.98, HTableInterface and RegionServerServices have a couple of new methods that must be implemented. 

The coprocessor code did not need updating yet, but binary compatibility for coprocessors between 0.96 and 0.98 versions is explicitly not guaranteed. 

Because the HBase 0.96 and 0.98 artifact names are the same, HBase dependency version management is moved into the compat module POMs. 

New 0.98 compat module tests pass:

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    T E S T S
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    Running com.continuuity.tephra.coprocessor.hbase98.TransactionVisibilityFilterTest
    Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.997 sec
    testFiltering(com.continuuity.tephra.coprocessor.hbase98.TransactionVisibilityFilterTest)  Time elapsed: 0.571 sec
    testTTLFiltering(com.continuuity.tephra.coprocessor.hbase98.TransactionVisibilityFilterTest)  Time elapsed: 0.11 sec
    Running com.continuuity.tephra.coprocessor.hbase98.TransactionDataJanitorTest
    Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 6.35 sec
    testTransactionStateCache(com.continuuity.tephra.coprocessor.hbase98.TransactionDataJanitorTest)  Time elapsed: 0.125 sec
    testDataJanitorRegionScanner(com.continuuity.tephra.coprocessor.hbase98.TransactionDataJanitorTest)  Time elapsed: 1.277 sec
    Results :
    Tests run: 4, Failures: 0, Errors: 0, Skipped: 0