removed the old Android app

Running git-annex linux builds in termux seems to work well enough that the
only reason to keep the Android app would be to support Android 4-5, which
the old Android app supported, and which I don't know if the termux method
works on (although I see no reason why it would not).
According to [1], Android 4-5 remains on around 29% of devices, down from
51% one year ago.

[1] https://www.statista.com/statistics/271774/share-of-android-platforms-on-mobile-devices-with-android-os/

This is a rather large commit, but mostly very straightfoward removal of
android ifdefs and patches and associated cruft.

Also, removed support for building with very old ghc < 8.0.1, and with
yesod < 1.4.3, and without concurrent-output, which were only being used
by the cross build.

Some documentation specific to the Android app (screenshots etc) needs
to be updated still.

This commit was sponsored by Brett Eisenberg on Patreon.

Utility/Yesod.hs

@@ -1,7 +1,6 @@
 {- Yesod stuff, that's typically found in the scaffolded site.
  -
- - Also a bit of a compatability layer to make it easier to support yesod
- - 1.1-1.4 in the same code base.
+ - Also a bit of a compatability layer for older versions of yesod.
  -
  - Copyright 2012-2014 Joey Hess <id@joeyh.name>
  -
@@ -13,28 +12,18 @@
 module Utility.Yesod 
 	( module Y
 	, liftH
-#ifndef __NO_TH__
 	, widgetFile
 	, hamletTemplate
-#endif
-#if ! MIN_VERSION_yesod_core(1,2,20)
-	, withUrlRenderer
-#endif
 	) where
 
 import Yesod as Y
 import Yesod.Form.Bootstrap3 as Y hiding (bfs)
-#ifndef __NO_TH__
 import Yesod.Default.Util
 import Language.Haskell.TH.Syntax (Q, Exp)
 import Data.Default (def)
 import Text.Hamlet hiding (Html)
-#endif
-#if ! MIN_VERSION_yesod(1,4,0)
 import Data.Text (Text)
-#endif
 
-#ifndef __NO_TH__
 widgetFile :: String -> Q Exp
 widgetFile = widgetFileNoReload $ def
 	{ wfsHamletSettings = defaultHamletSettings
@@ -44,7 +33,6 @@ widgetFile = widgetFileNoReload $ def
 
 hamletTemplate :: FilePath -> FilePath
 hamletTemplate f = globFile "hamlet" f
-#endif
 
 {- Lift Handler to Widget -}
 #if MIN_VERSION_yesod_core(1,6,0)
@@ -53,8 +41,3 @@ liftH :: HandlerFor site a -> WidgetFor site a
 liftH :: Monad m => HandlerT site m a -> WidgetT site m a
 #endif
 liftH = handlerToWidget
-
-#if ! MIN_VERSION_yesod_core(1,2,20)
-withUrlRenderer :: MonadHandler m => ((Route (HandlerSite m) -> [(Text, Text)] -> Text) -> output) -> m output
-withUrlRenderer = giveUrlRenderer
-#endif