Fixed coding style issues in Spark SQL

This PR addresses various coding style issues in Spark SQL, including but not limited to those mentioned by @mateiz in PR #146.

As this PR affects lots of source files and may cause potential conflicts, it would be better to merge this as soon as possible *after* PR #205 (In-memory columnar representation for Spark SQL) is merged.

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

Closes #208 from liancheng/fixCodingStyle and squashes the following commits:

fc2b528 [Cheng Lian] Merge branch 'master' into fixCodingStyle
b531273 [Cheng Lian] Fixed coding style issues in sql/hive
0b56f77 [Cheng Lian] Fixed coding style issues in sql/core
fae7b02 [Cheng Lian] Addressed styling issues mentioned by @marmbrus
9265366 [Cheng Lian] Fixed coding style issues in sql/core
3dcbbbd [Cheng Lian] Fixed relative package imports for package catalyst