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/user_test.go

@@ -39,19 +39,6 @@ func TestUserPreSave(t *testing.T) {
 func TestUserPreUpdate(t *testing.T) {
 	user := User{Password: "test"}
 	user.PreUpdate()
-
-	user.ThemeProps = StringMap{
-		"codeTheme":     "github",
-		"awayIndicator": "#cdbd4e",
-		"buttonColor":   "invalid",
-	}
-	user.PreUpdate()
-
-	if user.ThemeProps["codeTheme"] != "github" || user.ThemeProps["awayIndicator"] != "#cdbd4e" {
-		t.Fatal("shouldn't have changed valid theme props")
-	} else if user.ThemeProps["buttonColor"] != "#ffffff" {
-		t.Fatal("should've changed invalid theme prop")
-	}
 }
 
 func TestUserUpdateMentionKeysFromUsername(t *testing.T) {