Dependency Cleanup & Quicker Build Tweaks

[equk]

Removed Netlify-CMS React Plugin

Changed netlify-cms to use external pre-built js to speedup build times

• added admin/index.html to use pre-built netlify-cms from web
• removed postb script from build in package.json
• disabled unused postcss plugin lostgrid
• disabled unused plugins gatsby-remark-copy-linked-files & gatsby-remark-smartypants
• disabled plugin gatsby-plugin-netlify-cms to speed up build times

Fixed CSS Problems (purgecss)

• downgraded package gatsby-plugin-purgecss as completely ignoring rules set in config

Removed Dependencies

• removed unused dependency netlify-cms-app
• removed unused dependency gatsby-plugin-netlify
• removed unused dependency gatsby-plugin-netlify-cms
• removed unused dependency gatsby-remark-smartypants
• removed unused dependency gatsby-remark-copy-linked-files
• removed unused dependency lost
• remove unused dependency react-disqus-comments