[Qt-creator] Cmake plugin again

[Benjamin Zeller]

Hello all,

its been a while since we last merged the upstream CMake plugin
into our own Ubuntu-SDK codebase. As a result our current version
is behind the most recent QtC release.
Since the last merge there were a lot of things changed in the plugin
that makes it almost impossible to merge it again, so we decided to
start from scratch and since we have learned from the last time we
want to first propose the refactoring steps we are going to work on.

We decided to drop the idea of removing the "Run cmake" dialog but
still need a possibility to have a cmake per Kit.

So here are the steps, each one would be a self contained patch:

Patch 1:
-> Add a view to register multiple cmake instances to the system (in
    tools->options->Build&Run->cmake)
        * The user can select a default cmake tool that will be used for 
every build
        * do not add it to the Kit yet to keep the patch small
        * use a view like in the QtVersions settings page (treeview)
        * provide a central registry for all the cmake instances 
(CMakeToolManager)

Patch 2:
-> Make the cmake instances known to the Kits (CMakeKitInformation)
        * The run cmake dialog will pick up the cmake from the kit

Patch 1 is rather big, but I do not see a way to break it down even 
more, but
I'm open for suggestions :).

Daniel, can you please tell me if this proposal as the base of our 
implementation
is acceptable for you?

Regards,

Benjamin