Code restructure
Some refinements on the hadoop input format

This is a combination of commits:
* make hadoop-compat compatible to hadoop yarn and remove org.apache.hadoop code
* Extended usercode wrapper, fixed IF serialization
* introduce pluggable type converter
* make the converter interface more generic; (hopefully) improved fetching logic
Added convenience constructor to RemoteExecutor
Reorganized .gitignore.
quick fix for build error
Added code for reflective avro types.
Moving all annotations to Java API