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/main.cpp

@@ -108,7 +108,7 @@ int MSE::OnRun() {
 							parse_enum(String(argv[2]).substr(2), type);
 						}
 					}
-					Installer::installFrom(argv[1], true, isInstallLocal(type));
+//%%%					Installer::installFrom(argv[1], true, isInstallLocal(type));
 					return EXIT_SUCCESS;
 				} else if (arg == _("--symbol-editor")) {
 					Window* wnd = new SymbolWindow(nullptr);