When parsing git configs, support all the documented ways to write true and false, including "yes", "on", "1", etc.

This change does impact git-annex config
eg "git annex config --set annex.addunlocked on"
will store "on" and new git-annex will understand that value, while
old git-annex will error:
git-annex: bad annex.addunlocked configuration in git annex config:
Parse failure: near "on"
That seems acceptable.

Not special remote configs that are only documented as =true or =false
however. Having git-annex support other values for those would break
backwards compatability when used with old versions of git-annex. And
older versions ignore invalid special remote configs.. That would not
be a good combination.

Annex/SpecialRemote.hs

@@ -22,7 +22,6 @@ import Config
 import Remote.List
 import Logs.Remote
 import Logs.Trust
-import qualified Git.Config
 import qualified Types.Remote as Remote
 import Git.Types (RemoteName)
 
@@ -99,7 +98,7 @@ autoEnable = do
 			_ -> return ()
   where
 	configured rc = fromMaybe False $
-		Git.Config.isTrueFalse . fromProposedAccepted
+		trueFalseParser' . fromProposedAccepted
 			=<< M.lookup autoEnableField rc
 	canenable u = (/= DeadTrusted) <$> lookupTrust u
 	getenabledremotes = M.fromList