SPARK-1254. Supplemental fix for HTTPS on Maven Central

It seems that HTTPS does not necessarily work on Maven Central, as it does not today at least. Back to HTTP. Both builds works from a clean repo.

Author: Sean Owen <sowen@cloudera.com>

Closes #209 from srowen/SPARK-1254Fix and squashes the following commits:

bb7be47 [Sean Owen] Revert to HTTP for Maven Central repo, as it seems HTTPS does not necessarily work
[SPARK-1292] In-memory columnar representation for Spark SQL

This PR is rebased from the Catalyst repository, and contains the first version of in-memory columnar representation for Spark SQL. Compression support is not included yet and will be added later in a separate PR.

Author: Cheng Lian <lian@databricks.com>
Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #205 from liancheng/memColumnarSupport and squashes the following commits:

99dba41 [Cheng Lian] Restricted new objects/classes to `private[sql]'
0892ad8 [Cheng Lian] Addressed ScalaStyle issues
af1ad5e [Cheng Lian] Fixed some minor issues introduced during rebasing
0dbf2fb [Cheng Lian] Make necessary renaming due to rebase
a162d4d [Cheng Lian] Removed the unnecessary InMemoryColumnarRelation class
9bcae4b [Cheng Lian] Added Apache license
220ee1e [Cheng Lian] Added table scan operator for in-memory columnar support.
c701c7a [Cheng Lian] Using SparkSqlSerializer for generic object SerDe causes error, made a workaround
ed8608e [Cheng Lian] Added implicit conversion from DataType to ColumnType
b8a645a [Cheng Lian] Replaced KryoSerializer with an updated SparkSqlSerializer
b6c0a49 [Cheng Lian] Minor test suite refactoring
214be73 [Cheng Lian] Refactored BINARY and GENERIC to reduce duplicate code
da2f4d5 [Cheng Lian] Added Apache license
dbf7a38 [Cheng Lian] Added ColumnAccessor and test suite, refactored ColumnBuilder
c01a177 [Cheng Lian] Added column builder classes and test suite
f18ddc6 [Cheng Lian] Added ColumnTypes and test suite
2d09066 [Cheng Lian] Added KryoSerializer
34f3c19 [Cheng Lian] Added TypeTag field to all NativeTypes
acc5c48 [Cheng Lian] Added Hive test files to .gitignore
Merge branch 'master' into fixCodingStyle

Conflicts:
	sql/core/src/main/scala/org/apache/spark/sql/execution/Exchange.scala