Feature/issue 1103 remove boost format

#### Summary:

Refactored a lot of the error handling.
- Error messages and behavior should be the same.
- Removed dependency on the Boost format library.
- Reordered arguments of check functions to a consistent and sensible order.
- Changed `const char*` to `const std::string&` where appropriate.

#### Intended Effect:

This is the next step in the refactoring of the error handling. This step removed Stan's dependency on Boost's Format library (uses of `%1%` in the function name). In this pass, I also went through and ordered the input arguments to each of the check functions in the same order.

This pull request needs a spot check, but it doesn't make sense to go through every changed line. 

#### How to Verify:

See 
- `src/stan/error_handling/scalar/dom_err.hpp`
- `src/stan/error_handling/scalar/dom_err_vec.hpp`
to see how the messages are constructed now. 


#### Side Effects:

None. I've already gone through all places where arguments need to be changed.

For any open branches that need this merged, I can help.


#### Documentation:

Not user facing. In the next step, we're going to expose a bunch of functions to the user through the language. We'll need to document those.

#### Reviewer Suggestions: 

Anyone. It'll be better if this gets in sooner rather than later.

- [x] remove commented lines: `agrad/rev.hpp` `agrad/rev/internal.hpp` `model/model_header.hpp`
- [x] prefer `static const std::string function("stan::prob::dirichlet_log");` to `static const std::string function = "stan::prob::dirichlet_log";`
- [x] replace `while(` with `while (`
- [x] find as many includes in tests that aren't lexicographically ordered