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.

Assistant/WebApp/Configurators/Local.hs

@@ -165,13 +165,8 @@ postFirstRepositoryR :: Handler Html
 postFirstRepositoryR = page "Getting started" (Just Configuration) $ do
 	unlessM (liftIO $ inPath "git") $
 		giveup "You need to install git in order to use git-annex!"
-#ifdef __ANDROID__
-	androidspecial <- liftIO $ doesDirectoryExist "/sdcard/DCIM"
-	let path = "/sdcard/annex"
-#else
 	androidspecial <- liftIO osAndroid
 	path <- liftIO . defaultRepositoryPath =<< liftH inFirstRun
-#endif
 	((res, form), enctype) <- liftH $ runFormPostNoToken $ newRepositoryForm path
 	case res of
 		FormSuccess (RepositoryPath p) -> liftH $
@@ -180,12 +175,8 @@ postFirstRepositoryR = page "Getting started" (Just Configuration) $ do
 
 getAndroidCameraRepositoryR :: Handler ()
 getAndroidCameraRepositoryR = do
-#ifdef __ANDROID__
-	let dcim = "/sdcard/DCIM"
-#else
 	home <- liftIO myHomeDir
 	let dcim = home </> "storage" </> "dcim"
-#endif
 	startFullAssistant dcim SourceGroup $ Just addignore	
   where
 	addignore = do
@@ -392,10 +383,6 @@ driveList = mapM (genRemovableDrive . mnt_dir) =<< filter sane <$> getMounts
 		| dir == "/tmp" = False
 		| dir == "/run/shm" = False
 		| dir == "/run/lock" = False
-#ifdef __ANDROID__
-		| dir == "/mnt/sdcard" = False
-		| dir == "/sdcard" = False
-#endif
 		| otherwise = True
 #endif