How to create CV-fold index

[ikki407]

• previous version for CV-fold file. Using index.

train:

[2,3,4,5,6,7,8,9]

[0,1,4,5,6,7,8,9]

[0,1,2,3,6,7,8,9]

[0,1,2,3,4,5,8,9]

[0,1,2,3,4,5,6,7]

test:

[0,1]

[2,3]

[4,5]

[6,7]

[8,9]

• current version for CV-fold file(better than previous one). Using fold ID.

[0,0,1,1,2,2,3,3,4,4]

But current BaseModel uses previous version architectures.
If current version is used, it is changed to previous format.
So need to change that to using original format.
And need to change .ix to .iloc for stable behavior.

Need to change global CV-fold file name with new CV-fold file name, if new CV-fold be created.