mx documentation

[Mick Jordan]

There is some fledgling documentation on the mx tool available at 
https://wiki.openjdk.java.net/display/Graal/The+mx+Tool. It is also 
linked from the main Graal page.

I wrote this initially to spec the multiple suite support and the new 
commands that drive hg. However, my intention is that it is eventually 
complete and accurate for all commands, including those in the extension 
suites such as graal. So far I have documented all the built-in 
commands, to varying degrees.

Feedback is welcome.

On the multiple suite support: If you are developing code that either 
extends Graal, e.g. a new backend, or uses Graal, that you would prefer 
to keep separate, then this is now possible. The mx suite support 
essentially makes the separation transparent when it comes to 
development, including in an IDE. If you have questions that the 
documentation does not address, please contact me via the list of directly.

Mick