Fix TVG rendering

[felix-schwarz]

• Extend TVG and MakeTVG with new "viewBox" attribute
• Extend TVGImage to support "viewBox" attribute to correctly render whitespace on the right and bottom of vector images (was previously not honored)

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[codecov]

Codecov Report

Merging #124 into master will increase coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #124      +/-   ##
==========================================
+ Coverage   29.63%   29.74%   +0.11%     
==========================================
  Files          64       64              
  Lines        5669     5678       +9     
==========================================
+ Hits         1680     1689       +9     
  Misses       3989     3989

Impacted Files	Coverage Δ
ownCloud/Theming/TVG/TVGImage.swift	82.6% <100%> (+1.47%)	⬆️

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[jesmrec]

Only one detail about pic's thumbnails:

they fit cell height without padding. Comparing with same view in web UI:

maybe it is something to do in a different issue/PR

CC @felix-schwarz

[felix-schwarz]

@jesmrec That's actually unrelated to SVG/TVG rendering.

The thinking between showing icons and thumbnails that led to this choice is this:

• icons that are as large as the thumbnails feel huge and (to me, at least) don't feel right to the point that it looks like a bug
• thumbnails as small as the icons feel too small and offer too little space to be of much use

That's why, right now, the app displays icons at a smaller size than thumbnails. I'm of course open to change and discussing this in a separate issue.

[jesmrec]

i did not think in a bug for such behaviour, for me it is ok to discuss in a new issue.

This one is approved on my side.