Added "WithMode" function variants.  Use "fmap" in place of "either".

Deprecation messages in Language.Haskell.Meta.Parse said not to use "myDefaultParseMode" or "myDefaultExtensions", and while they were still exported, there was no simple way to not use them by providing your own variants to the parse functions.  Instead, replicating chunks of the library was required.  I also simplified a lot of the code while I was at it.

It took me a few attempts to get this change set separated out from my other change set (hence the repeated reversions), but I've got it sorted now.  The two are entirely independent (though both directly related to my needs - one allows me to specify "TypeFamilies", the other parses type family declarations.