Update Giraph-Gora documentation and make it available from giraph.a.o
GIRAPH-947: Compilation error with hadoop 2.5.x fixed.

1. Munge symbol 'STATIC_SASL_SYMBOL' was added.
2. STATIC_SASL_SYMBOL was added to all build profiles, except hadoop_2 and hadoop_snapshot. Profile 2.1.1-SNAPSHOT is not munge-free anymore.
3. Default hadoop version of profile hadoop_2 was changed: 2.2.0 -> 2.5.0
GIRAPH-946. Upgrade to Gora 0.5 (Renato Javier Marroquín Mogrovejo via rvs)
Fix using aggregators before aggregation

Summary:
If we register aggregator and immediatelly ask for aggregated value,
previous code was returning initial value, so we have to do the same.

Additionally - cleaning up errors/exceptions to be more understandable
(vs NullPointerEx for example)

Test Plan:
mvn install
AggregatorsBenchmark and ReducersBenchmark

Reviewers: majakabiljo, pavanka, sergey.edunov, maja.kabiljo

Differential Revision: https://reviews.facebook.net/D24951
Auto-restart from checkpoint doesn't pick up latest checkpoint

Summary:
While running different jobs with checkpoints enabled I noticed some issues:
1) The way we pick up latest checkpoint is not correct. Current implementation just picks whatever is returned last from FileSystem.list(), which is not necessarily the last checkpoint
2) If job restarts from checkpoint it immediately creates another checkpoint.
3) We need more flexibility in GiraphJobRetryChecker to allow restarts after multiple failures.

Test Plan: Run our production jobs with checkpointing

Reviewers: majakabiljo, pavanka, pavanka.26, maja.kabiljo

Reviewed By: maja.kabiljo

Differential Revision: https://reviews.facebook.net/D23913
GIRAPH-956. disable tests for a few components in hadoop_2 profile
GIRAPH-958. .arcconfig needs to be added to rat exclude
GIRAPH-960: Max task attempts should be 1 and not 0.

Summary: 0 is an invalid number that may not work on some Hadoop distributions

Test Plan: Ran a job and failed a task.

Reviewers: pavanka.26, maja.kabiljo

Reviewed By: maja.kabiljo

Differential Revision: https://reviews.facebook.net/D27579
Allow vertex/edge/message value to be configurable

Summary: And throw if WritableUtils.createWritable(clazz) is called with GiraphConfigurationSettable.

Test Plan: mvn install

Reviewers: sergey.edunov, pavanka, maja.kabiljo

Reviewed By: maja.kabiljo

Differential Revision: https://reviews.facebook.net/D25353
Fix removal of MasterLoggingAggregator

Test Plan:
mvn clean install

How should I test this?

Reviewers: pavanka, maja.kabiljo

Reviewed By: maja.kabiljo

Differential Revision: https://reviews.facebook.net/D27651
GIRAPH-963 Aggregators may not be initialized properly

Summary: Aggregators may fail with IllegalArgumentException upon deserialization

Test Plan: Run same job

Reviewers: majakabiljo, pavanka, pavanka.26, maja.kabiljo

Reviewed By: maja.kabiljo

Differential Revision: https://reviews.facebook.net/D28227
GIRAPH-964: Remove quotes from output partition specification in hive-io
Merge branch 'trunk' of https://github.com/apache/giraph into trunk
Merge branch 'trunk' into biiig-testing