add kdenlive icon, improve inkscape icon

icon for Kdenlive video editor, following kdenlive's guidelines for sizes lower than 50px.

icon for Inkscape

• based upon the official Inkscape logo
• made in all 6 sizes
• more clarity, better pixel-fitting and contrast than the current elementaryPlus icon:

Thank you for your PR, which is a great first contribution!

The Kdenlive icon is missing the pictrogram shadow. Edit: Apparently it's optional, so it's fine unless you think a pictogram shadow would look better.

On the Inkscape icon the pictogram shadow is missing the stroke ("Create a copy of this shadow and give it a 1 pixel stroke (also black) and adjust this element to 7% opacity."). Also the border radius (at least for the 128 px version) is smaller than on the Kdenlive icon. The correct value for 128px should be 6px.

I hope this doesn't sound too critical and I am aware that some current icons also have faults, but I want to make sure elementary+ follows the elemenatary HIG as close as possible. Greetings from the Speckgürtel ;)

What happen to this repository? No one seems to be working on it anymore.

Sadly I believe mank319 is not using elementary anymore, which is also true for me and other contributors. And while we had some testers and users, there was always a lack of actual icon designers. In addition, elementary OS 0.4 broke most of the work on indicators. This makes it quite hard to maintain this project.