KIJIMR-171. Refactor build artifacts for multiple Hadoop distributions.

Add initial platform bridge modules.
* Shim Fixes discrepancy between TaskAttemptID c'tors.
  (In CDH4 it takes a TaskType; in hadoop1 it takes 'boolean isMap'.)

Create modules for hadoop-1.x build and full KijiMR distribution.
* Compiles the kiji-mapreduce module again, against hadoop 1.x, in a separate module.

Create separate 'dist' module.
dist/ module creates the final "release" tarball
* includes KijiMR dependencies in lib/
* moves KijiMR jar to lib/distribution/hadoop2/

Adjusts how DistributedCacheJars is written so it compiles in both environments
without shimming.

Get correct artifacts deployed:
* existing kiji-mapreduce artifact renamed kiji-mapreduce-hadoop2
* moved kijimr-hadoop1x/ module to mr-hadoop1x/ (artifact: kiji-mapreduce-hadoop1)
** note: this is disabled.
* dist/ module artifact is kiji-mapreduce
** Attaches kiji-mapreduce-hadoop2.jar as kiji-mapreduce w/ hadoop2 classifier.
** Attaches kiji-mapreduce-hadoop1.jar as kiji-mapreduce w/ hadoop1 classifier.
** Depends on kiji-mapreduce-hadoop2.pom, so projects depending on kiji-mapreduce:jar
   include all our non-provided dependencies.
** Eliminated need for kiji-mapreduce[-hadoop2]:distribution:tar.gz
** Move jars into assembly with fileSets, not dependencySets to avoid passing
   transitive dependencies on both jars to our clients.
** Add provided-scope dependency on kiji-schema to dist module.
* Fixed checkstyle error in KijiMR introduced earlier in this process.
* Disabled hadoop1 build for now so this can build "green."

Tested with mvn clean install...
Then changed kiji-music to depend on kiji-mapreduce 1.0.0-rc61-SNAPSHOT.
* 'mvn clean verify' works
* 'mvn dependency:tree' shows correct inherited jars.