[TYPO3-project-4-3] invalid markup in BE

[Steffen Kamper]

Hi,

by examine the HTML of BE pages tidy validator find a lot of 
errors/warnings.

* oncontextmenu - this is a double of onclick, also this is IE only and 
not needed, so it can be safely removed
* nested forms - found in page module
* xhtml and & - it's used in URLs very often and can be replaced with &

I will do some cleanup patches, any further comments?

vg Steffen