[SPARK-3974][MLlib] Distributed Block Matrix Abstractions

This pull request includes the abstractions for the distributed BlockMatrix representation.
`BlockMatrix` will allow users to store very large matrices in small blocks of local matrices. Specific partitioners, such as `RowBasedPartitioner` and `ColumnBasedPartitioner`, are implemented in order to optimize addition and multiplication operations that will be added in a following PR.

This work is based on the ml-matrix repo developed at the AMPLab at UC Berkeley, CA.
https://github.com/amplab/ml-matrix

Additional thanks to rezazadeh, shivaram, and mengxr for guidance on the design.

Author: Burak Yavuz <brkyvz@gmail.com>
Author: Xiangrui Meng <meng@databricks.com>
Author: Burak Yavuz <brkyvz@dn51t42l.sunet>
Author: Burak Yavuz <brkyvz@dn51t4rd.sunet>
Author: Burak Yavuz <brkyvz@dn0a221430.sunet>

Closes #3200 from brkyvz/SPARK-3974 and squashes the following commits:

a8eace2 [Burak Yavuz] Merge pull request #2 from mengxr/brkyvz-SPARK-3974
feb32a7 [Xiangrui Meng] update tests
e1d3ee8 [Xiangrui Meng] minor updates
24ec7b8 [Xiangrui Meng] update grid partitioner
5eecd48 [Burak Yavuz] fixed gridPartitioner and added tests
140f20e [Burak Yavuz] Merge branch 'master' of github.com:apache/spark into SPARK-3974
1694c9e [Burak Yavuz] almost finished addressing comments
f9d664b [Burak Yavuz] updated API and modified partitioning scheme
eebbdf7 [Burak Yavuz] preliminary changes addressing code review
1a63b20 [Burak Yavuz] [SPARK-3974] Remove setPartition method. Isn't required
1e8bb2a [Burak Yavuz] [SPARK-3974] Change return type of cache and persist
239ab4b [Burak Yavuz] [SPARK-3974] Addressed @jkbradley's comments
ba414d2 [Burak Yavuz] [SPARK-3974] fixed frobenius norm
ab6cde0 [Burak Yavuz] [SPARK-3974] Modifications cleaning code up, making size calculation more robust
9ae85aa [Burak Yavuz] [SPARK-3974] Made partitioner a variable inside BlockMatrix instead of a constructor variable
d033861 [Burak Yavuz] [SPARK-3974] Removed SubMatrixInfo and added constructor without partitioner
49b9586 [Burak Yavuz] [SPARK-3974] Updated testing utils from master
645afbe [Burak Yavuz] [SPARK-3974] Pull latest master
b05aabb [Burak Yavuz] [SPARK-3974] Updated tests to reflect changes
19c17e8 [Burak Yavuz] [SPARK-3974] Changed blockIdRow and blockIdCol
589fbb6 [Burak Yavuz] [SPARK-3974] Code review feedback addressed
aa8f086 [Burak Yavuz] [SPARK-3974] Additional comments added
f378e16 [Burak Yavuz] [SPARK-3974] Block Matrix Abstractions ready
b693209 [Burak Yavuz] Ready for Pull request