Robot: allow meta modifier

[bill]

Add support the meta modifier to typeKeys(), in addition to ctrl, alt, and shift, so that tests can do commands like this on mac:

doh.robot.typeKeys("a", {meta: true});

(to select all the text)

[bill]

(In [18533]) Support meta modifier to keyPress(), in addition to ctrl, alt, and shift. This is so we can write tests that run on mac.

Also added in some notes on building DOHRobot on mac.

Fixes #9491 !strict.

[bill]

(In [18628]) Missed a function call to update with new parameter for meta key support. Refs #9491 !strict.

[bill]

(In [18837]) Fix comment, refs #9491 !strict.