PackageInstaller: Improved main window layout

 * Moved "Install to:" besides the "Install" button again.
 * Don't right-align menu field labels.
 * Give the install type description some default text when no description is
   given. Give it a smaller font, align with the type menu.
BMenuField: Draw everything on resize

 * The label might be truncated, in which case the entire width needs to be
   redrawn when the menu field shrinks or grows.
 * Invalidating the border in the parent looked a bit weird. Simplified.
PackageInstaller: Handle aborting the file panel

 * Select the first item and reset the path.
PackageInstaller: More robust way to select destination...
... after file panel is cancelled.
PackageInstaller: Disable debug output of scripts
PackageInstaller: Ignore uninstall-error before install