[Enhancement] Replace icons with vector icons

[elipriaulx]

The icons are currently rasters; adding new features that rely on icons and buttons requires rasters similar of a similar fit and such, and as TumblThree is a developer-led project, there is a huge overhead in effort finding something appropriate.

By using an open-source-friendly icon font (like glyphs in bootstrap, or font-awesome) we can immediately have access to a pool of consistent icons and that remove this overhead. Furthermore, doing so will make the application look better on resolution-scaled devices and large low resolution monitors.

I suggest moving to use Font Awesome. It is open source friendly, has an updating pool of icons, and there is a nuget package that exposes these a strongly typed Wpf UserControl.

https://fontawesome.com/license/free https://fontawesome.com/icons?d=gallery https://github.com/charri/Font-Awesome-WPF/?FontAwesome.WPF=4.7.0.9

If TumblThree outgrows Font Awesome, there are tools like http://fontastic.me which allow custom fonts to be composed using other icon fonts, and downloaded, which could be combined with a form of Charri's WPF package.

[elipriaulx]

It looks like Segoe UI Symbol font is used in ImageResources.xaml; the plot thickens...

[elipriaulx]

Once PR #350 is merged or abandoned, I will submit a PR for this, specifically updating the CrawlerView.xaml. Resolution of #350 is a requisite due to 'unmergable' conflicts in the view layout.

Before:

After:

You may not like the resize behaviour. I kept it similar, but it isn't the same due to changing the view structure to make it less verbose.