A logfile is now generated by default, in the format `.embark/embark-log__YYYY-MM-DD_HH-mm-ss.log`.
When the home tab is loaded, the process logs are fetched for all the processes. The list of processes returned now includes `embark`, and when `/embark-api/process-logs/embark` is fetched, the logFile is parsed and an array of log messages are returned.
* Add loglevel and logfile switch to `embark build`
* Support existing `loglevel` and `logfile` switch for `embark run/upload`
* make casing consistent for `loglevel` and `logfile`
* remove passing engine to `build()` and instead pass needed objects in options.
* prevent duplicate plugin initiation (above point)
* allow `Events` object to be passed to `Engine` constructor and `init()`
* prevent echo of upload commands to allow interception and control via logging
