Isolate non-returning functions in new tasks

[runeharlyk]

Purpose

When updating firmware, making the device sleep or restarting, the server does not get the chance to respond as the request handling function never returns.
By wrapping the non-returning functionality in tasks, the server can respond with an OK status before eg. restarting.

esp_err_t UploadFirmwareService::uploadComplete(PsychicRequest *request)
{
(...)
    if (!request->_tempObject)
    {
        request->reply(200);
        RestartService::restartNow(); 
        return ESP_OK; // Before this could not be reached
    }
}