rename methods of min and max that do reductions to minimum and maximum

this is step 1 for #4235
Merge branch 'master' of github.com:JuliaLang/julia into jb/minmax
step 2 for #4235

make minimum and maximum use scalarmin and scalarmax, which are min
  and max but exclude arrays

remove isless for AbstractArray

add LexicographicOrdering and use it in sortrows and sortcols
currently LexicographicOrdering is implemented with cmp(), which does
  the right thing for arrays, but we might not want to keep it that way
update release notes for min/max changes
Merge branch 'master' of github.com:JuliaLang/julia into jb/minmax
add lexcmp and lexless for lexicographic comparison

step 3 of #4235, closes #4235
Merge branch 'master' of github.com:JuliaLang/julia into jb/minmax

Conflicts:
	base/ordering.jl