Let bikes use Envirosuit + Shield

[Elver]

As it currently stands, bikers can never have armor better than padded E-suits, which gives them a limited shelf life. Additionally, Personal Shields are an expensive sidegrade - if not downgrade - for most units that can currently use them. It seems like there would be synergy (and a certain degree of logic) in letting bikes use shields, and doing so would give them some (very) late-game relevance they currently lack.