Rest specification does not match swiML

[hazzery]

swiML models all forms of rest as a child element of an instruction. Currently, swimDSL does this for rest since start, but not rest after stop. Furthermore, swiML has four different types of rest but swimDSL currently only has two (missing are since last rest and in out). The grammar should be modified to have all four rest types as child nodes of the instruction node.

A potential way of creating such a syntax may look like the following:

150 Freestyle rest 0:30  # after stop
150 Freestyle on 1:15  # existing behavior for since start
150 Backstroke in-out 3  # thee in one out
150 Breaststroke since 0:30  # since last rest (I don't quite understand this concept)