Add basic browser and platform into to changeset tags

[bhousel]

This adds some simple info to the changeset tags about browser and platform used.
Reporting this info is useful for some things (see #2449).

• Browser version is detected as major.minor only (no patch included).
• Platform is very simple (Windows/Macintosh/Linux) with no version.
• These fields are namespaced with 'iD:' to not conflict anything

Looks like this in practice:

cc @pnorman

[pnorman]

If the tags aren't iD specific and are clear in their meaning, I think avoiding namespaces are best.

P2 can run on multiple sites, and all editors have a locale. Browser is less relevant for P2, but any future HTML or JavaScript editors will probably find it relevant.

[bhousel]

hmm.. platform is already a key.. Maybe change to operating_system and remove the namespaces?

[pnorman]

hmm.. platform is already a key

Used in changeset tags?

[ImreSamu]

statistics: https://gist.github.com/ImreSamu/0fc3b8015e6dd16595c5

[tilmanb]

This does seem odd. If we cant detect anything, we set the detected os to windows? Why?

[bhousel]

detected.os is used for only one thing in iD, and that is to setup the keyboard shortcuts in cmd.js.

I suppose win was just picked as a conservative default for the keyboard shortcut setup. In reality, if the code runs here, the user is probably on a device without a keyboard - like a game console or an Android phone.