The device configuration widget is now the only place the user
ever has to specify ports.

This is necessary in case there is no run configuration (e.g. for
library projects).

... because the files are installed even when packaging is disabled.

Reviewed-by: kh1

Doesn't do anything yet.

This removes the all hard dependencies to and from welcome screen,
except the one to the core plugin. More in detail:

- Add IWelcomePage to add a tab to the welcome screen
- Move tabs in the modules where they belong
- Enables QHelpManager to open help fullscreen and contextually
- "Getting Started" moves to Qt4ProjectManager
- Projects & Sessions (aka "Develop") moves to ProjectExplorer
- "Community" remains in the welcome plugin for simplicity

Details: Moving files so that the local layout corresponds to the layout pushed by make install.
Adjust Make target, modify the resource path of the loader to find the resources in the
right place. All pathes are still looked up relative to binaryPath(), libs are found via
relative rpath.