Icon and pictogram tooling and updates

[joshblack]

We have several categories of updates needed for Icons and Pictograms that need to be addressed for both design and development. These updates include:

• Add pictogram generation logic to Sketch plugin
  • Update kit to include pictograms
• Address icon rendering issues in Sketch plugin
  • Update kit to include fixed icons
  • Update override structure of color styles within a icon symbols
• Update kit to include new batch of icons
  • We might need to publish the plugin for each release for this purpose
• Handle deprecation for icons and correctly warn when using a deprecated asset
• Address common build problems when using icons (namely tree-shaking and overall size)
• Update colors to use a space between "/" naming structure