Allow user to send bug report from settings screen

app/src/main/res/values/constants.xml

@@ -21,5 +21,6 @@
     <string name="helpURL">https://isoron.github.io/uhabits/faq.html</string>
     <string name="playStoreURL">market://details?id=org.isoron.uhabits</string>
     <string name="feedbackURL" formatted="false">mailto:isoron+habits@gmail.com?subject=Feedback%20about%20Loop%20Habit%20Tracker</string>
+    <string name="bugReportURL" formatted="false">mailto:isoron+habits@gmail.com?subject=Bug%20Report%20-%20Loop%20Habit%20Tracker</string>
     <string name="sourceCodeURL">https://github.com/iSoron/uhabits</string>
 </resources>

app/src/main/res/values/strings.xml

@@ -148,4 +148,7 @@
     <string name="import_data_summary">Supports full backups exported by this app, as well as files generated by Tickmate, HabitBull or Rewire. See FAQ for more information.</string>
     <string name="export_as_csv_summary">Generates files that can be opened by spreadsheet software such as Microsoft Excel or OpenOffice Calc. This file cannot be imported back.</string>
     <string name="export_full_backup_summary">Generates a file that contains all your data. This file can be imported back.</string>
+    <string name="bug_report_failed">Failed to generate bug report.</string>
+    <string name="generate_bug_report">Generate bug report</string>
+    <string name="troubleshooting">Troubleshooting</string>
 </resources>

app/src/main/res/xml/preferences.xml

@@ -65,6 +65,17 @@
 
     </PreferenceCategory>
 
+    <PreferenceCategory
+        android:key="pref_key_debug"
+        android:title="@string/troubleshooting">
+
+        <Preference
+            android:key="bugReport"
+            android:title="@string/generate_bug_report">
+        </Preference>
+
+    </PreferenceCategory>
+
     <PreferenceCategory
         android:key="pref_key_links"
         android:title="@string/links">