Add Colour to Insert Mathtex

[wbrenna]

In util/LatexAction.cpp a colour option could be added to choose the Mathtex colour.

[wbrenna]

Also, locate the cursor and place the inserted mathtex there if a new equation is being edited.

[andreasb242]

Already possible, e.g. write \color{red}red

Therefore i close this, because of age

[alexeymuranov]

Latex tool wishlist #1115:

Rendered font color should be the color selected in the toolbar