Add the DISABLED state to form controls

[alorenzen]

TS pull requrest: angular/angular#10994
TS Design Doc: https://docs.google.com/document/d/1k_iYcgTS1cDJkyXvBWQZGPlkWZhEqAVphC0xyKSAqPs/edit

[chalin]

IMHO this is also related to added support for form reset (I thought that there used to be an issue open for form reset but I can't find it atm).

[alorenzen]

Yes, it is. Both have been added to the 5.0 milestone, as I'm planning to work on both in the next few weeks.

[chalin]

Nice! Is there still an issue that can use to track the progress of form reset?

[alorenzen]

#216