LaTeX curly brackets do not convert correctly

[SubjunctiveQuaver]

I've noticed that LaTeX curly brackets do not convert correctly (according to standard LaTeX editing rules).

Fails: $\{STUFF\}$ [correct LaTeX syntax] -> \({STUFF}\) [appears wrong, as "STUFF"]
Works: $\\{STUFF\\}$ [wrong LaTeX syntax] -> \(\{STUFF\}\) [appears correct, as "{STUFF}"]

Ideally, the correct LaTeX syntax results in the correct display/conversion in Anki; right now adding an extra backslash works, but is not accurate LaTeX syntax.

[Yandrik]

\lbrace STUFF \rbrace fails too, because the \r gets translated as a line break.

[duguosheng]

I have tried to fix these errors these days, my pr is not be merged now, you can download new version here and help me to test it.
Besides \{\}, some other character errors have also been fixed(\#\$\&\_\\)