Remove deprecated Pool/Share statistic models. The information is stored in
smart manager models.
Attributes such as pool and share sizes, usage etc.. must be BigIntegerFields
to accommodate values more than 2TB.
Change various IntegerFeilds to BigIntegerFields in smart manager that can be
larger than 2TB.
Merge pull request #432 from schakrava/issue_431_BigIntegerField

Issue 431 big integer field