Reorganize project structure

## Help

- μlogger's current status is shown by two leds, one for location tracking and one for web synchronization: 

led | tracking | synchronization

-|-------- | ---------------

![status green](https://dummyimage.com/10/00ff00) |  on, recently updated | synchronized

![status yellow](https://dummyimage.com/10/ffe600) | on, long time since last update | synchronization delay

![status red](https://dummyimage.com/10/ff0000) | off | synchronization error

| led                                                | tracking                        | synchronization       |

|----------------------------------------------------|---------------------------------|-----------------------|

| ![status green](https://dummyimage.com/10/00ff00)  | on, recently updated            | synchronized          |

| ![status yellow](https://dummyimage.com/10/ffe600) | on, long time since last update | synchronization delay |

| ![status red](https://dummyimage.com/10/ff0000)    | off                             | synchronization error |

- clicking on current track's name will show track statistics

package net.fabiszewski.ulogger;

class Logger {

    static final boolean DEBUG = true;

public class Logger {

    public static final boolean DEBUG = true;

}

        android:enableOnBackInvokedCallback="true"

        android:dataExtractionRules="@xml/data_extraction_rules">

        <activity

            android:name=".MainActivity"

            android:name=".ui.MainActivity"

            android:exported="true">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

        <activity android:name=".SettingsActivity" />

        <activity android:name=".ui.SettingsActivity" />

        <service

            android:name=".LoggerService"

            android:name=".services.LoggerService"

            android:enabled="true"

            android:exported="false"

            android:foregroundServiceType="location" />

        <service

            android:name=".WebSyncService"

            android:name=".services.WebSyncService"

            android:exported="false"

            android:foregroundServiceType="dataSync"/>

import androidx.activity.result.contract.ActivityResultContracts;

import androidx.annotation.NonNull;

class CreateGpxDocument extends ActivityResultContracts.CreateDocument {

public class CreateGpxDocument extends ActivityResultContracts.CreateDocument {

    public static final String GPX_MIME = "application/gpx+xml";

import androidx.core.content.ContextCompat;

import androidx.preference.PreferenceManager;

import net.fabiszewski.ulogger.db.DbAccess;

import net.fabiszewski.ulogger.services.LoggerService;

import net.fabiszewski.ulogger.services.WebSyncService;

import net.fabiszewski.ulogger.ui.AutoNamePreference;

import net.fabiszewski.ulogger.ui.SettingsActivity;

public class ExternalCommandReceiver extends BroadcastReceiver {

    private static final String START_LOGGER = "start logger";