PGF export

["Cong Kien Dang" <kiendc gmail com>]

Hi all,
I ve tried modify a litle in PGF export plugins 
- in tex_escaps_string. I changed in such a way that it could keep the mathematical formula in the text like $\alpha \leq \beta$. It's done.
- In draw_string(), I would like to modify the aligment but it do nothing, I don't know why every text is exported with anchor=WEST
- I would lke to add a dialog to set some parameter of exporting like the variable du (by default it is always 15/unitlength, we may want to 10/unitlength for example) or scale ...
Anyone know to do it
Thank
Kien