WICKET-5677 add onReAdd to Component

Squashed commit of the following:

commit fab66e85410c14b7a0ede5c953e315a7e5143e3d
Merge: 10d83d2 c728d89
Author: Carl-Eric Menzel <cmenzel@wicketbuch.de>
Date:   Sat Sep 27 19:35:52 2014 +0200

    Merge branch 'wicket-6.x' into WICKET-5677

commit 10d83d2932c53dd165dbcc4c3f226f4597c142de
Author: Carl-Eric Menzel <cmenzel@wicketbuch.de>
Date:   Tue Aug 26 23:38:17 2014 +0200

    WICKET-5677 readd should only be called after a remove, never before

commit 0a8e964f1a3c3226f52ab22137455acf55f45c74
Merge: 055958a 3a5648b
Author: Carl-Eric Menzel <cmenzel@apache.org>
Date:   Mon Aug 25 07:41:06 2014 +0200

    Merge branch 'wicket-6.x' into WICKET-5677

commit 055958a9c60db45d96c1828803dbee37e5926678
Author: Carl-Eric Menzel <cmenzel@wicketbuch.de>
Date:   Mon Aug 25 07:23:57 2014 +0200

    add re_added flag

commit 348e9dbc899c3a62eccf7c50739162b0c0be63c2
Merge: 40c4210 c3eb7e2
Author: Carl-Eric Menzel <cmenzel@wicketbuch.de>
Date:   Fri Aug 22 00:29:16 2014 +0200

    Merge remote-tracking branch 'github/WICKET-5677' into WICKET-5677

    Conflicts:
    	wicket-core/src/main/java/org/apache/wicket/Component.java
    	wicket-core/src/main/java/org/apache/wicket/MarkupContainer.java

commit c3eb7e24954d3909c74201682dba5e4de8fcadd4
Author: Carl-Eric Menzel <cmenzel@apache.org>
Date:   Mon Aug 18 14:08:16 2014 +0200

    WICKET-5677 clean up tests

commit 4703c1ae1af91fdcca44e34edbeeb8bbaeb63b6c
Author: Carl-Eric Menzel <cmenzel@apache.org>
Date:   Mon Aug 18 13:35:44 2014 +0200

    WICKET-5677 change onadd to onReAdd and only call when oninitialize wouldn't be called

commit 70b7327d2ce142707171cd31a1b612cffaa7a066
Author: Carl-Eric Menzel <cmenzel@apache.org>
Date:   Mon Aug 18 11:27:24 2014 +0200

    added javadoc

commit 9a6ba692a48b76c30ead6915d4bc43275a255b3c
Author: Carl-Eric Menzel <cmenzel@wicketbuch.de>
Date:   Mon Aug 18 10:42:33 2014 +0200

    WICKET-5677: add onAddToPage lifecycle event

commit 40c42104f9882b938dd84e8469f2922efebd2ce3
Author: Carl-Eric Menzel <cmenzel@wicketbuch.de>
Date:   Mon Aug 18 10:42:33 2014 +0200

    WICKET-5677: add onAddToPage lifecycle event