Export image in a vector format

[KonradHoeffner]

Feature request

Description of new feature

Export image in a vector format, such as SVG.

Motivation for new feature

I have a large graph that I want to print on a poster. While exporting as PNG works, the maximum resolution is limited (see #1943) and unless the resolution exactly matches that of the printer, the quality is not optimal. Because of that, exporting a vector format would be perfect, e.g. as cy.svg() analogous to cy.png() and cy.jpg().

[maxkfranz]

See

nrnb/GoogleSummerOfCode#61

#639

The GSOC project did not get selected.