Vcpkg: Initial commit

This introduces the vcpkg support plugin. Initial features are:

- Options page for defining vcpkg installation location
- Search dialog for searching/selecting a package
  (incl. parsing autotest)
- TextEditor that shows search/options toolbuttons
- File wizard that creates a vcpkg.json manifest

Change-Id: I098784100c869e0bb2ed6f60db4dedad559a142a
Reviewed-by: hjk <hjk@qt.io>

src/plugins/plugins.qbs

@@ -84,6 +84,7 @@ Project {
         "todo/todo.qbs",
         "updateinfo/updateinfo.qbs",
         "valgrind/valgrind.qbs",
+        "vcpkg/vcpkg.qbs",
         "vcsbase/vcsbase.qbs",
         "webassembly/webassembly.qbs",
         "welcome/welcome.qbs",