* Continue work started by patcon in #2272 for importing slack again and again without duplicates. Currently errors out. Also fixed #2532 for Slack and HipChat.

* Ignore new slack channel format

* Add ability to upsert messages on sendMessage

* Show a better error for duplicated oembed records

* Add function to handle errors

* Delete message errors

* handle error for hideRoom

* Allow returning error instead of calling toastr.error

* Handle error for leaveRoom

* handle error for openRoom

* handleError for toggleFavorite

* handleError in updateMessage

* error for samlLogout

* handleError for assets

* Add global handleError to eslint

* handleError for addOAuthService

* handleError: getUserRoles

* handleError: insertOrUpdateUsere

* handleError: messageDeleting

* handleError: removeUserFromRoles

* handleError: addPermissionToRole

* handleError: addUserToRole

* handleError: deleteRole

* handleError: removeRoleFromPermission

* handleError: removeUserFromRole

* handleError: saveRole

* Return ready on publish without permission

* handleError: channel-settings

* handleError: mailMessages

* handleError: fileUpload

* handleError: rocketchat-importer

* handleError: addIncomingIntegration

* handleError: deleteIncomingIntegration

* handleError: updateIncomingIntegration

* handleError: addOutgoingIntegration

* handleError: deleteOutgoingIntegration

* handleError: updateOutgoingIntegration

* Return ready on publish without permission

* handleError ldap

* remove throw from client code

* handleError: setEmail, slashCommand

* Sort en.i18n.json

* Google translated languages

* Use correct error return from publishes

* RateLimiter.limitFunction

* Fix order of error "500"

* handleError validateEmailDomain

* handleError channelSettings; settings

* handleError livechat

* handleError: Mailer.sendMail

* handleError pinMessage and unpinMessage

* handleError messageStarring

* handleError oauth apps

* handleError: saveNotificationSettings

* handleError getRoomRoles

* handleError: createDirectMessage

* handleError saveUserPreferences

* handleError: saveUserProfile

* handleError sendConfirmationEmail

* Add ecmascript to root

Improve the stability of the importers, reject invalid uploaded files when they don't contain any users, channels, or messages.

Greatly extend the import framework. Implemented the new framework into the slack import and added HipChat import, two examples of how to use the import framework

Move the importer to it's own package. Add the slack importer, first version that is missing a few message types and attachments. Need to clean up the ui and add a loading/processing screen.