ConfigurableExtension(PreferenceScreen) support (#163)

* initial PreferenceScreen support, works with 'NeoXXX Scans' (pt-br)

* convert EditTextPreference to json successfully

* commit what I've got

* bring back the old SharedPreferences for CustomContext, implement Toast

* put back syer's implementation

AndroidCompat/src/main/java/xyz/nulldev/androidcompat/io/AndroidFiles.kt

@@ -26,6 +26,8 @@ class AndroidFiles(val configManager: ConfigManager = GlobalConfigManager) {
     val downloadCacheDir: File get() = registerFile(filesConfig.downloadCacheDir)
     val databasesDir: File get() = registerFile(filesConfig.databasesDir)
 
+    val prefsDir: File get() = registerFile(filesConfig.prefsDir)
+
     val packagesDir: File get() = registerFile(filesConfig.packageDir)
 
     fun registerFile(file: String): File {