Generalize OperandsAndPartials

[PeterLi2016]

Generalize OperandsAndPartials so it works for probability distributions with forward mode and reverse mode auto-diff.

Distribution Test fixtures:

• Update test_fixture_distr
• Update test_fixture_cdf
• Update test_fixture_cdf_log
• Update test_fixture_ccdf_log

New tests to add:

• add higher order diff tests for inc_beta [no need to do grad_inc_beta since we're testing this already here]
• add higher order diff tests for grad_reg_inc_beta
• add higher order diff tests for F32
• add higher order diff tests for grad_F32
• add higher order diff tests for grad_2F1
• add higher order diff tests for grad_reg_inc_gamma

Other:

• rename DoubleVectorView to VectorBuilder
• fix make file for clean-all (issue make clean-all Error 126 #697)
• change algorithm for generating test cases so doubles are not repeated

[PeterLi2016]

Everything is in this branch: https://github.com/stan-dev/stan/tree/feature/issue-676-generalize-operandsandpartials.

I think I've got OperandsAndPartials generalized and working with the prob functions (I've only fixed normal_log so far). So how do we want go about testing? I'd imagine we want to follow something similar to what Daniel already has implemented for the rev probability functions.