Feature/issue 1122 remove policy

#### Summary:

Removing the remaining boost policy references.
Fixed the reverse mode implementation of `check_pos_definite.hpp` and added tests. These weren't working before.

#### Intended Effect:

Goal was to remove the remaining places where boost policy was being referenced. In doing so, found that `check_pos_definite` wasn't working. Fixed that.

#### How to Verify:

Search for `policy` or `Policy`. The only reference now is to ISERP inside the documentation.

#### Side Effects:

None. This should have been removed a long time ago.

#### Documentation:

Fixed. Removed in both the reference manual and doxygen.

#### Reviewer Suggestions: 

Anyone.
Why is this commented out?