[Qt-creator] Qt Creator now uses Qt 5 plugin metadata

[Ziller Eike]

If you are building Qt Creator from the master branch, you need to do a clean recompile (after pulling).

With  https://codereview.qt-project.org/93360 Qt Creator uses the Qt 5 plugin meta data instead of the custom .pluginspec files to find information about plugins.
That means that instead of .pluginspec(.in) files, the same data needs to be provided in .json(.in) files now, and the information is compiled into the plugin library instead of being kept as an extra file.

-- 
Eike Ziller, Senior Software Engineer - Digia, Qt
 
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