Rename hadoopReduce -> groupReduce

Also rename combinableReduce -> combinableGroupReduce
Fixed problems with scripts and default config

- added missing environment variables in scripts
- changed default port of web frontend back to 8080
- replaced bc command with 'expr +' for adding heap sizes
Added toString() methods to configuration and task classed to ease debugging.
prevent chained tasks in the iteration tail for now.
Fixed Stratosphere Website link (relative relative to absolute link)

[ci skip]
Change scala KMeans now that map as last op in interation works
Reworked input channels with respect to returning events and buffers. Simplified logic and fixed bugs and reduced number of status polls.
Reworked record readers to properly support unions and events.
Fixed Nephele Visualization job selection not working on Mac OS X

[ci skip]
Fixed and extended comments in WorksetConnectedComponents example.
[ci skip]
fixed: PactRecord allocating too few memory when writing UTF encoded strings
Upload builds as tgz and as directory to DOPA server
Fix stratosphere-dist: Some really outdated README's removed. The README and LICENCE were not copied to the build.
Fixed overly restrictive condition to identify disjoint plans.
Rename groupReduce -> reduceGroup, add reduce/reduceAll on DataStream
Moved pact-compiler-tests from individual project into pact-tests.