Don't send `rev` when deleting a Bot

[czechboy0]

• - routes_bot.js - app.delete(k.XCSAPIBasePath + '/bots/:id/:rev?', prepareRequest, verifyIfServiceIsEnabledAllowCertificate, enforceBotCreatorRole, botClass.remove.bind(botClass));
  Seems like we might not need to send the rev any more when deleting a bot. Try and remove the rev if it works.
• - up the compatibility version from 5 to 6