Improve Unknown tags error handling.

[flacohenao]

One of the things I've noticed is that, whenever a tag is unkown this error is thrown:

{ generalStatusCode: 4, extendedStatus: [ 0 ] }

This is not really usefull, because instead of saying which variable is failing... it throws this message but all the other variables can not be read, and we get a bunch of nulls.

it should be nice to have the conflicted variable with some specific status or null and the other ones performing the readings. if this is not possible, at least improve the error so we can know what is happening.

This can be reproduces adding an unexisting tag.

Also, not having this can lead us to a memory leak eventually due to multiple listeners set and undestroyed in the underlayer of the emitter like so:

(node:16260) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 Multiple Service Packet listeners added to [Controller]. Use emitter.setMaxListeners() to increase limit

[GeekMeUpScotty]

@SerafinTech @flacohenao I believe this issue can be closed as of recent merge (#58).