Updating docs with boolean array indexing and nonzero order. 

Small docs update of boolean indexing in the user and reference manuals and at *np.nonzero* to close #3177. Also adding links to *row-major* and *column-major* terms where found. 
Are you bikeshedding [1]?

Trying to unify the terminology for "C order", "C-like", "C-style" and
other variants.

[1]
https://en.wikipedia.org/wiki/Parkinson%27s_law_of_triviality