Cut down on a bunch of one-offs of install(new *Module() {...}) by
choosing a more appropriate base module class. This doesn't solve all
such cases, for example RpcServletModule must still inherit from
ServletModule, but it does clean up some code. (And who knows, fewer
modules may even mean faster startup time.)
Change-Id: Ie1aed05d0a64f7f11b121c9a637bb30d80e9a595