Implement missing API in pyspark.

MLUtils
* appendBias
* loadVectors

`kFold` is also missing however I am not sure `ClassTag` can be passed or restored through python.

Author: lewuathe <lewuathe@me.com>

Closes #5707 from Lewuathe/SPARK-6263 and squashes the following commits:

16863ea [lewuathe] Merge master
3fc27e7 [lewuathe] Merge branch 'master' into SPARK-6263
6084e9c [lewuathe] Resolv conflict
d2aa2a0 [lewuathe] Resolv conflict
9c329d8 [lewuathe] Fix efficiency
3a12a2d [lewuathe] Merge branch 'master' into SPARK-6263
1d4714b [lewuathe] Fix style
b29e2bc [lewuathe] Remove scipy dependencies
e32eb40 [lewuathe] Merge branch 'master' into SPARK-6263
25d3c9d [lewuathe] Remove unnecessary imports
7ec04db [lewuathe] Resolv conflict
1502d13 [lewuathe] Resolv conflict
d6bd416 [lewuathe] Check existence of scipy.sparse
5d555b1 [lewuathe] Construct scipy.sparse matrix
c345a44 [lewuathe] Merge branch 'master' into SPARK-6263
b8b5ef7 [lewuathe] Fix unnecessary sort method
d254be7 [lewuathe] Merge branch 'master' into SPARK-6263
62a9c7e [lewuathe] Fix appendBias return type
454c73d [lewuathe] Merge branch 'master' into SPARK-6263
a353354 [lewuathe] Remove unnecessary appendBias implementation
44295c2 [lewuathe] Merge branch 'master' into SPARK-6263
64f72ad [lewuathe] Merge branch 'master' into SPARK-6263
c728046 [lewuathe] Fix style
2980569 [lewuathe] [SPARK-6263] Python MLlib API missing items: Utils