small doc fixes
CDK-175: Adding support for Parquet with Hive, Impala.

This adds utiltiites to convert from Avro schemas to Hive column
descriptions, FieldSchema and TypeInfo. This also adds serde and
inputformat/outputformat class metadata to the convertion maps for
Parquet. Both Hive and Impala work with a simple record test schema.

For testing, it was necessary to exclude the versions of hive and hadoop
parquet-hive from parqet-hive's dependencies. The hcatalog module no
longer depends on parquet-hive, but adding the exclusion will prevent
needing to figure it out later.
Adding initial View interface and Marker class.

Also added PartitionStrategy#keyFor(Marker) and changed the Field
partitioners so that the source type is accessible. This is necessary
when calling Marker#getAs(name, type) with source fields.
Adding experimental MarkerRecord
Adding better documentation, range end types.

This adds toBefore(Marker) and fromAfter(Marker), which create open
range end-points.
Adding PartitionKey comparison to PartitionStrategy.

PartitionStrategy now implements Comparator<PartitionKey> and
FieldPartitioner<S,T> implements Comaparator<T>. Strategies rely on the
FieldPartitioners to compare each field in a given key.

PartitionKeys are not Comparable because the comparison only has
relevance within a given PartitionStrategy. In addition, PartitionKeys
produced by different PartitionStrategies would potentially fail with
IllegalArgumentException when runtime types do not match, or may simply
produce useless comparison results.
CDK-177: Updating the View interface.

* Removing unnecessary public modifiers
* Updated getCoveringPartitions to return Iterable<View>
CDK-177: Adding #newKey to PartitionStrategy.

This returns an empty PartitionKey that is the right size.
CDK-177: Adding AbstractDataset, fixing the FS impl.

AbstractDataset implements many of the View methods, throwing
NotSupportedException for backward-compatibility.