[SECURITY] Unsafe unserialize of GET parameter in Add-Wizard

If the TCEforms wizard "add" is used, the original opened document
is closed and a new one is created in which you then add a new
element to be related.

In order to "store" the originating document which has been
edited, the Wizard/AddController and EditDocumentController
exchange state data in an URL-parameter.

This state-array is serialized in the EditDocumentController
and again unserialized in the Wizard/AddController from that
GET parameter. Without any checks, every code can be injected
to be unserialized here - even though we just need an array
with some data.

This patch changes serialize/unserialize to json_encode and
json_decode. Since the GET parameter only is used in
conjunction of these two classes it is save to changes the
format how the URL parameters are serialized.

Change-Id: I4d3d0915a90647ec6cf08a86c73533ab2159a828
Fixes: #54073
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Security-Commit: 9790d0e627d94c0efad600e451c3e7e10584028b
Security-Bulletin: TYPO3-CORE-SA-2013-004
Reviewed-on: https://review.typo3.org/26206
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader
[SECURITY] Remove possible XSS from ActionController Error output

As parameters passed to an ErrorObject can be user input, the
output of those parameters in the ActionController::errorAction() method
could lead to a cross side scripting possibility.

The offending output has been removed without substitution.

Change-Id: Iada1546a16fe6877edab42ca9a4a1a01574c29e0
Fixes: #54074
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Security-Commit: c3fa68afcdaa4322451d37b8b6a9a0a90f2df8d0
Security-Bulletin: TYPO3-CORE-SA-2013-004
Reviewed-on: https://review.typo3.org/26207
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader