Finally got precompiled headers to work.

Now all C++ files need to #include <util/prec.hpp>
 That is why all .cpp files are touched by this commit

Many changes to installers and update checking:
     - the window is now called PackagesWindow, in a new source file
     - update checking is now independent from the PackagesWindow. For update checking only a list of package versions are needed (vector<PackageDependency>). This is much less information to download at each startup.
     - the list of available packages is now a list of available Installers, since an installer can contain multiple packages.
     - moved the logic of dependency checking etc. to data/installer
     - moved the actual installation to util/io/package_manager
     - moved directory iteration/creation logic to util/file_utils
     - added PackageDirectory: the local and global package directory now have their own object (was part of PackageManager)
     - added PackageVersion: for detecting if a package has been modified after it was installed.
     - added PackageDescription: description/header of a package. Basicly the same as what Packaged provides.
     - added DownloadableInstaller: where to find an insaller, what does it contain?
     - added InstallablePackage: brining it all together: installer, package, status, action.

Current status: the insaller is currently broken in a few places, more on that soon.

git-svn-id: svn://svn.code.sf.net/p/magicseteditor/code/trunk@792 0fc631ac-6414-0410-93d0-97cfa31319b6

src/gui/control/gallery_list.cpp

@@ -6,6 +6,7 @@
 
 // ----------------------------------------------------------------------------- : Includes
 
+#include <util/prec.hpp>
 #include <gui/control/gallery_list.hpp>
 #include <gfx/gfx.hpp>
 #include <wx/dcbuffer.h>
@@ -91,7 +92,6 @@ void GalleryList::scrollTo(int top, bool update_scrollbar) {
 	top = max(0, top);
 	// scroll
 	if (top == visible_start) return;
-	//%int old_top = visible_start;
 	visible_start = top;
 	if (update_scrollbar) {
 		// scroll bar