Give warnings if dupe account created:

* Check for existing accounts with matching servername + username
* Show a dialog and block account creation
* Triggers in three cases:
  * After input of an auto-setup account (e.g. Gmail or AOL)
  * After input of manual setup (incoming) parameters
  * After changing incoming parameters of *any* existing account
* Made some notes in EmailContent regarding fields in HostAuth that we
    are not actually using.
* Added HostAuth unit tests

Primarily fixes bug # 1964449
Bonus fix for bug # 1594408

Change-Id: I49310faf6654280582e0ab3d3e40f2701bfcd21d
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 7f431d3..8f405c0 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -271,6 +271,13 @@
     <!-- Toast when we can't build a URI from the given email & password -->
     <!-- Note, the error message in the toast is purposefully vague, because I *don't* know exactly what's wrong. -->
     <string name="account_setup_username_password_toast">Please type a valid email address and password.</string>
+    <!-- Title of dialog shown when a duplicate account is created -->
+    <string name="account_duplicate_dlg_title">Duplicate Account</string>
+    <!-- Message of dialog shown when a duplicate account is created.  The display name of
+         the duplicate account is displayed. -->
+    <string name="account_duplicate_dlg_message_fmt">
+        This login is already in use for the account \"<xliff:g id="duplicate">%s</xliff:g>\".
+    </string>
 
     <!-- Do Not Translate.  Activity Title for check-settings screen -->
     <string name="account_setup_check_settings_title"></string>