Optionally increase the size of rendered latex

[Mikael]

When working on a high-res screen, I have to increase the text size in zim quite a bit (15 points is about the right size for me). However, I write quite a few equations which are not scaled size-wise accordingly.

The result is that I have to manually run ImageMagick to scale up all the generated png files.
<strike>That's doable if I have a small number of equations on a given page, but over time it's a nightmare to keep track of which ones have been scaled up already.</strike> (Strike that, I just realized I could rename the scaled images to something obvious)

It would still be a nice thing not to require the extra step, though.

[Mikael (mikael79+launchpad)]

For me, adding a flag to the dvipngcmd tuple in plugins.equationeditor.py seems to work as a workaround:

-dvipngcmd = ('dvipng', '-q', '-bg', 'Transparent', '-T', 'tight', '-o')
+dvipngcmd = ('dvipng', '-q', '-D', '180', '-bg', 'Transparent', '-T', 'tight', '-o')

For general use, the `180` should probably be settable, but I am, for the moment, happy with my hardcoded value.