Revert "Qbs: Add new 'extra' generator for qbs project files"

This reverts commit f85db2f323.

Discussion by the QtCreator community at

  https://bugreports.qt.io/browse/QTCREATORBUG-13695

raises concerns about this particular approach to working with CMake
projects using QtCreator.  Also, the functionality and design of the QBS
extra generator was never discussed on the CMake mailing list or with
QtCreator developers.  There may be better ways to make the two tools
work together.

In order to avoid committing to long-term support of this generator
prior to such discussion taking place, revert it from CMake for now.
We may restore this or use an alternative design based on results of
such discussion.

Help/generator/Qbs.rst

@@ -1,25 +0,0 @@
-Qbs
----
-
-Generates Qbs project files.
-
-Project files for Qbs will be created in the top directory and
-in every subdirectory which features a CMakeLists.txt file containing
-a PROJECT() call.  Additionally a hierarchy of makefiles is generated
-into the build tree.  The appropriate make program can build the
-project through the default make target.  A "make install" target is
-also provided.
-
-This "extra" generator may be specified as:
-
-``Qbs - MinGW Makefiles``
- Generate with :generator:`MinGW Makefiles`.
-
-``Qbs - NMake Makefiles``
- Generate with :generator:`NMake Makefiles`.
-
-``Qbs - Ninja``
- Generate with :generator:`Ninja`.
-
-``Qbs - Unix Makefiles``
- Generate with :generator:`Unix Makefiles`.

Help/manual/cmake-generators.7.rst

@@ -110,4 +110,3 @@ The following extra generators are known to CMake.
    /generator/KDevelop3
    /generator/Kate
    /generator/Sublime Text 2
-   /generator/Qbs

Help/release/dev/add-extra-qbs-generator.rst

@@ -1,6 +0,0 @@
-add-extra-qbs-geneator
-----------------------
-
-* It is now possible to generate :generator:`Qbs` project files
-  for use with QtCreator IDE, matching make tool must be used
-  to build the project through the generated makefiles.