Updates to `boards.txt` file

[PixnBits]

It looks like the 1.5.x branch of the Arduino IDE has an updated boards.txt

I've edited ide-1.5.x_boards.txt to keep existing data and merge in new data from the specified file. The result is in my main branch: https://github.com/PixnBits/arduino-data/

Of note is that the vid and pid data is root level and that they go in pairs (ex: see uno.json)

I think it's important to be able to merge in new data from updated boards.txt files, but it seems we need more intelligence than I've added to do so properly (hence no PR).

Thoughts?

[joshmarinacci]

I'm okay with manually adding new boards from boards.txt. The official IDE isn't updated very often and they haven't decided if people should be using the 1.0 or 1.5 IDE, even after several years. I don't care that they changed the format slightly because we will likely support new boards before they do.

[PixnBits]

Sounds good, of the new files (atmegang.json, megaADK.json, yun.json) we've discussed megaADK in #8, I think yun.json should be added, and IDK about atmegag.json as it seems to be a placeholder for older boards.

[joshmarinacci]

Yeah. Leave out the older boards for now. If it's important some one will ask for it.

[PixnBits]

Right, will close after adding yun.