Reactivated the "fresh install" code in the Bootscript, but modified it

a bit:
* Added directory /etc/post_install, which can contain scripts that will
  be executed on the first boot.
* Moved the mimeset invocations to such a script. Use the "-apps"
  option instead of "-all". Since create_app_meta_mime() (and thus
  mimeset) work recursively now, running the commands does actually have
  an effect.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25309 a95241bf-73f2-0310-859d-f6bbb57e9c96

data/etc/post_install/fresh_install

@@ -0,0 +1 @@
+This file is only supposed to exist on fresh Haiku installations.

data/etc/post_install/mime_update.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+# Make sure all apps have a MIME DB entry.
+
+mimeset -apps -f /boot/beos/apps
+mimeset -apps -f /boot/beos/preferences
+mimeset -apps -f /boot/beos/system/servers
+mimeset -apps -f /boot/apps