Generate error when uploading detection files as Receiver Events

[xhoenner]

A user recently mis-uploaded three csv detection files through the upload receiver event page instead of the upload tag detection page.

Doing so didn't return an error for the user during the upload, which suggests there's a lack or absence of constraints on files that can be uploaded through the receiver event webpage. Worse, when digging in a bit deeper my investigations showed that the content of those detection files had been populated into the receiver_event table.

To be done:

• when users upload detection files through the receiver event page the system should return an error so that users are aware they've made a mistake and are prompted to re-upload those files through the tag detection page.
• when an error is generated by the system, the detection files don't get uploaded into the receiver_event page.

[xhoenner]

For future references, here's an example of a receiver event file

Date/Time	Receiver	Description	Data	Units
2016-02-08 23:31:44	VR2W-114415	Initialization	114415
2016-02-08 23:31:44	VR2W-114415	PC Time	2016-02-09 10:31:44 UTC+11:00
2016-02-08 23:31:44	VR2W-114415	69 kHz decoding map	MAP-113
2016-02-08 23:31:44	VR2W-114415	69 kHz blanking interval	260	ms
2016-02-08 23:50:57	VR2W-121137	Initialization	SN_121137
2016-02-08 23:50:57	VR2W-121137	PC Time	2016-02-09 10:50:57 UTC+11:00
2016-02-08 23:50:57	VR2W-121137	69 kHz decoding map	MAP-113
2016-02-08 23:50:57	VR2W-121137	69 kHz blanking interval	260	ms
2016-02-08 23:59:59	VR2W-114415	Daily Pings on 69 kHz	0
2016-02-08 23:59:59	VR2W-114415	Daily Syncs on 69 kHz	0
2016-02-08 23:59:59	VR2W-114415	Daily Rejects on 69 kHz	0

And here's one of a tag detection file

Date and Time (UTC)	Receiver	Transmitter	Transmitter Name	Transmitter Serial	Sensor Value	Sensor Unit	Station Name	Latitude	Longitude
2016-02-15 03:22:54	VR2W-114410	A69-9002-8773			30	ADC	114410
2016-02-15 03:27:51	VR2W-114410	A69-9002-8773			31	ADC	114410
2016-02-15 03:35:19	VR2W-114410	A69-9002-8770			21	ADC	114410
2016-02-15 03:37:32	VR2W-114410	A69-9002-8770			27	ADC	114410
2016-02-15 03:39:42	VR2W-114410	A69-9002-8772			16	ADC	114410
2016-02-15 03:40:04	VR2W-114410	A69-9002-8770			18	ADC	114410
2016-02-15 03:43:04	VR2W-114410	A69-9002-8770			17	ADC	114410
2016-02-15 03:44:43	VR2W-114410	A69-9002-8771			31	ADC	114410
2016-02-15 03:45:56	VR2W-114410	A69-9002-8773			33	ADC	114410
2016-02-15 03:46:13	VR2W-114410	A69-9002-8770			27	ADC	114410