Support for transposing local matrices added. The `.transpose` function creates a new object re-using the backing array(s) but switches `numRows` and `numCols`. Operations check the flag `.isTransposed` to see whether the indexing in `values` should be modified.

This PR will pave the way for transposing `BlockMatrix`.

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #4109 from brkyvz/SPARK-5321 and squashes the following commits:

87ab83c [Burak Yavuz] fixed scalastyle
caf4438 [Burak Yavuz] addressed code review v3
c524770 [Burak Yavuz] address code review comments 2
77481e8 [Burak Yavuz] fixed MiMa
f1c1742 [Burak Yavuz] small refactoring
ccccdec [Burak Yavuz] fixed failed test
dd45c88 [Burak Yavuz] addressed code review
a01bd5f [Burak Yavuz] [SPARK-5321] Fixed MiMa issues
2a63593 [Burak Yavuz] [SPARK-5321] fixed bug causing failed gemm test
c55f29a [Burak Yavuz] [SPARK-5321] Support for transposing local matrices cleaned up
c408c05 [Burak Yavuz] [SPARK-5321] Support for transposing local matrices added