distributed pushed down joins - more testing

have now written and pushed ndbapi testing of our push-down join implementation (~2k LOC)

the following classes/programs was added

• HugoQueryBuilder (class)
  Construct a pseudo-random query
  inputs: a list of tables and a options specifying which features should be used in query
• HugoQueries (class)
  Run an arbitrary query.
  Note: Does only verify individual rows, not relations/result-set. For verifying result-sets we use random query generator
• testSpj (program)
  Ndbapi test-program using above classes to runs various tests for our cluster specific automatic testing framework
• hugoJoin (program)
  Stand-alone test-program that takes list of tables/options as command-line arguments
  and using above classes constructs/runs random queries

Quite happy with this, as it's very much needed to get good coverage of the implementation,
especially error cases (e.g node-failure) which is hard to test from/with SQL.

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And please provide feedback on preview release that we made!