Improve overall exception handling and error feedback to the user

The main goals of this patch are to:
- Improve the exception handling in Aegis and the way we present errors messages
  to the user when they occur.
- Write exception stack traces to the log in more places, so that the ADB logs
  we ask for from our users when reporting bugs become more useful.
- Reduce the amount of times we throw a RuntimeException, particularly when an
  Android Keystore operation fails.

Achieving the above goals ended up resulting in a very large refactor. The
intro and unlock flow of the app need to be retested entirely.

app/src/main/java/com/beemdevelopment/aegis/ui/EditEntryActivity.java

@@ -165,7 +165,7 @@ public class EditEntryActivity extends AegisActivity {
             _textCounter.setText(Long.toString(((HotpInfo) info).getCounter()));
             _rowCounter.setVisibility(View.VISIBLE);
         } else {
-            throw new RuntimeException();
+            throw new RuntimeException(String.format("Unsupported OtpInfo type: %s", info.getClass()));
         }
         _textDigits.setText(Integer.toString(info.getDigits()));
 
@@ -204,7 +204,7 @@ public class EditEntryActivity extends AegisActivity {
                         _rowCounter.setVisibility(View.VISIBLE);
                         break;
                     default:
-                        throw new RuntimeException();
+                        throw new RuntimeException(String.format("Unsupported OTP type: %s", type));
                 }
             }
 
@@ -510,7 +510,7 @@ public class EditEntryActivity extends AegisActivity {
                     info = new HotpInfo(secret, algo, digits, counter);
                     break;
                 default:
-                    throw new RuntimeException();
+                    throw new RuntimeException(String.format("Unsupported OTP type: %s", type));
             }
 
             info.setDigits(digits);