Refactor ToolChains in Qt Creator:
* Allow for several toolchains of the same type
* Be smarter wrt. guessing what kind of output a toolchain
produces. This allows us to eventually handle e.g. embedded
linux setups way better than before.
* Be smarter wrt. guessing what kind of environment a Qt version
needs.
* Improve auto-detection of toolchains a bit
* Decide on which debugger to use based on the kind of output
produced by the compiler.
* Add options page to configure toolchains
* Remove toolchain related options from the Qt version dialog
Reviewed-by: dt