Reorganize the Preferences

[sspanak]

After completing #151, #155, #156 and #159, the main Preferences screen will become too long. In order not to overwhelm the user with so many options at once, let's put some of them on new screens and only have links to the new screens on the main screen.

• New structure is as follows:
  • (no changes) Help
  • (category -> new screen) Appearance
    • Contains "Dark Theme", "On-screen keys" and any new settings from Add toast display of input mode #155 and Add an on-screen numpad for use on any smartphone #159.
  • (category -> new screen) Dictionaries
    • (no changes) Languages
    • (rename) Load Dictionaries -> Load Selected
    • (new) Clear Selected (clears the database only for the selected languages)
    • (rename) Clear Dictionaries -> Clear All
    • (new) Update the "Dictionary Hints" section in the user manual.
  • (category -> new screen) Keyboard
    • (no changes) Select Hotkeys
      • (new) Make sure navigating back from this one, navigates to "Keyboard", not to the main screen.
      • (new) Add a "Change Theme key" hotkey option. Keep it unassigned by default. Dropping this in favor of using a "combo", when keypad navigation is enabled.
    • (new option) Add the new option from Add support for Microsoft Bluetooth number pad #151.
    • (new category, if Add ABC mode timeout for same-key characters #156 is completed) ABC Mode
    • (no changes) Predictive Mode. The same as before, just move it from the main screen.
  • (no changes) About

Dropping these:

• Allow keypad navigation, like in Nokia 6303:
  • Pressing a number key selects the respective option.
  • Add key hints in front of the respective option. The Nokia displays them above the scroll, but this is not possible on Android. If it is too difficult to find a place for the index, just skip it.
  • If in doubt, use the Nokia as an example.

[sspanak]

Dropping everything the hotkey requirement.

It is possible to do it using onKeyUp() in the PreferencesActivity, then passing the key to the BaseScreenFragment and from there using getPreferenceScreen().getPreference(i).performClick();. However this method fails, after pressing Back, to go to the previous screen, because the PreferenceManager becomes null for unknown reasons. Debugging took too much time without any promissing results, so it is no longer worth the effort. I may come back to this in the future, when I have more time.