Implemented 3G USB dongle setup CLI command

[bart]

This commit implements a simple way of configuring 3G USB dongles which automatically gets detected by OpenWrt. It has been tested with a HUAWAI E173.

You can use the command like this:

t2 3g --config --apn="" --dialnumber="" --username="" --password="" => Configure network and enable 3G connection
t2 3g --on => Enable 3G connection
t2 3g --off => Disable 3G connection
t2 3g --status => Print 3G connection status information

[tessel-bot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @rwaldron (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[bart]

Resolves #541

[coveralls]

Coverage decreased (-1.5%) to 84.524% when pulling 90428e6 on bart:feature/3g into 73739db on tessel:master.

[coveralls]

Coverage decreased (-1.5%) to 84.524% when pulling 90428e6 on bart:feature/3g into 73739db on tessel:master.

[HipsterBrown]

This is a great start! 👏 I have a few suggestions to match the coding style of this repo and expected command interface based on the existing t2 wifi and t2 ap commands.

Do you know if you are able to connect to the 3g network and start an access point at the same time?

I can help out with creating some tests for this command if you're new to nodeunit.

Let me know if you have any questions

[HipsterBrown]

Can you update the use of var in this file to const? Those variables are never reassigned so we can optimize with the use of const.

[HipsterBrown]

There appears to be a typo here.

Suggested change

	return this.configure3gDongle(apn. dialnumber, username, password);
	return this.configure3gDongle(apn, dialnumber, username, password);

[HipsterBrown]

Similar to the wifi and ap commands, I would expect configuration to be the default mode of the 3g command. For example:

t2 3g --apn="" --dialnumber="" --username="" --password=""

I would expect that command alone to configure the Tessel to connect to that 3g network and be enabled.

If none of those configuration options are passed in, i.e. t2 3g, I would expect to see the current configuration and status of 3g mode. Just like if you use t2 wifi, the cli will return the current details of the Tessel's wifi connection (if it is connected).