Correct composer.json

Composer "replace" part is not correct. 
See https://wiki.typo3.org/Composer for more info.
At the current state, an extension directory "tinymce4-rte" is generated.
After this change it's "tinymce4_rte".

See merge request !9

Fix negativ pid when doing a positioned insert

If you insert a content element (or a page) at a concrete position
f.e. after content element 15 the value in $row['pid'] is -15.

But in $this->data we already have the real pid, so we can just use it.

See merge request !7

Add multiple contentCSS support



See merge request !8