PLT-2992 Added the ability to use different themes for each team (#3411)

* Cleaned up user_settings_theme.jsx and import_theme_modal.jsx

* Made ImportThemeModal use a callback to return the theme to the user settings modal instead of saving it directly

* Moved user theme from model to preferences

* Added serverside API to delete preferences TODO update package with client stuff

* Changed constants.jsx so that Preferences and ActionTypes can be imported on their own

* Updated ThemeProps migration code to properly rename solarized code themes

* Fixed warnings thrown by AppDispatcher

* Added clientside UI to support team-specific themes

* Removed debugging code from test

* Fixed setting a user's theme when they haven't set their theme before

model/client.go

@@ -1556,6 +1556,16 @@ func (c *Client) GetPreferenceCategory(category string) (*Result, *AppError) {
 	}
 }
 
+// DeletePreferences deletes a list of preferences owned by the current user. If successful,
+// it will return status=ok. Otherwise, an error will be returned.
+func (c *Client) DeletePreferences(preferences *Preferences) (bool, *AppError) {
+	if r, err := c.DoApiPost("/preferences/delete", preferences.ToJson()); err != nil {
+		return false, err
+	} else {
+		return c.CheckStatusOK(r), nil
+	}
+}
+
 func (c *Client) CreateOutgoingWebhook(hook *OutgoingWebhook) (*Result, *AppError) {
 	if r, err := c.DoApiPost(c.GetTeamRoute()+"/hooks/outgoing/create", hook.ToJson()); err != nil {
 		return nil, err