Add constexpr begin(), end(), cbegin(), cend() to FixedArray, Index, Offset, and Size#3236

hjmjohnson merged 4 commits intoInsightSoftwareConsortium:masterInsightSoftwareConsortium/ITK:masterfrom

N-Dekker:FixedArray-Index-Offset-Size-begin-end-constexprN-Dekker/ITK:FixedArray-Index-Offset-Size-begin-end-constexprCopy head branch name to clipboard