refactor .border-radius to use .border-*-radius mixins
added .glow inspired by dmitryf/elements PR#62

only change is that the optional argument (@blur) is placed AFTER the
required argument (@color)
.selection added with inspiration from dmitryf/elements PR#48

css selectors were combined to DRY up the less
comment renamed
Organized .transition* mixins
Added .transition-property
Added .transition-timing-function
Added .transition-delay
organize and coding arg arity correctly with semicolons