PDF/LaTex: Enable *.sty and *.cls overrides

[hsk81]

The Sphinx back-end employs a few preset styles *.sty an classes *.cls to define default "templates"; if people want to modify these they can't since they remain hidden in the back-end during conversion.

It should be possible to enable a flag during project creation to also show these template files inside the project. Further if somebody creates a corresponding folder with file(s) that matches default style/class file(s), then the user defined file(s) should override the defaults!

[hsk81]

The last time I tried, Sphinx was very stubborn and kept overriding my user provided files and it was impossible to figure out when to override the default styles/classes; check if this is still the case.