[Qt-creator] Time to update sdktool's README.

[Christian Gagneraud]

Hi folks,

The sdktool home page [1] seems like it needs a serious brush up:
- The examples still refer to the old "ini" files, not the XML ones.
- The option arguments have certainly changed.
- Things have changed a lot since Qt Creator 2.6.
- What about Qbs?
- What about CMake? (don't care right now, but it might change)
- What about qmake? (don't care right now, but it might change)
- What about target devices?
- What about gdb? (the doc says it's managed with addQt)
- And what about any custom tool running on the target device?

I want to use the sdktool to manage my own kits in an automated way
and I found this README very useful, but yet very outdated.

I wouldn't mind to submit an update on gerrit, it looks like things
have changed quite a lot.

Any comment, advices, warnings, yes-go, no-go, ... ?

Chris

[1] https://github.com/qt-creator/qt-creator/tree/master/src/tools/sdktool