latex.xml is dead, long live latex.xml.

We (the kile devs) decided to remove our own syntax files for latex and bibtex from kile and instead use only the ones from kate.
So we confuse the users less and also have never two versions lying around.
The nice update mechanism in kate also helps a lot :)

The changes are as follows:
- support all biblatex cite commands (partially #179849)
- fix highlightning of @{...} in tabular environment arguments (#179367)
- subref, subref* and cref/cref* added
- support all newcommands, providecommands, renewcommands and also their starred version
- treat \iffalse .. \else \fi as comment
- add commands \KileResetHL and \KateResetHL in comments. They change the syntax back to "Normal Text". Especially useful after cases where the standard syntax highlightning fails.

example:
<command which leaves syntax highlightning in math mode> % \KileResetHL
<new text correctly highlighted>

- add support for ensuremath{}
- allow @ in commands
- tabularx added
- correctly display bullet in some math environments
- add limited support for $$ in \text and \intertext in math environments.