Improve layout blocks

[robyngit]

Some layout blocks that are not otherwise included in a GitHub issue need either minor style and layout improvements, updates to front matter templates, or both:

• checklist - needs to be updated to use the line icons that are used elsewhere in the page. Consider making the icons configurable for each item, and/or merging this block with the "features-list" block
• disqus - if Disqus will still be used for webinars, this block needs to be tested, styled, and requires a front matter template
• icon - The icon block uses custom icon svgs that are currently stored in the partials/icons directory. These should be moved to the icon block folder and the front matter template needs to be updated to include a list of icon options
• line-icon - This block uses feather icons. It needs a front matter template which should include a select field listing all possible icon options. Consider merging this with the icon block
• image - needs to be updated to use the getImage function and should add options that make use of Hugo's image processing functionality (e.g. allow a user to set max height or max width of an image). Any blocks that include images should be updated to use this block as a partial instead (e.g. the logos-bar block)
• item-with-icon - This block is similar to the simple-feature block and can probably be combined
• map - This block is so far not used anywhere and is a WIP, but could be used to show a map given longitude and latitude. If we'll use it, it needs a front matter template, styles, and the layout needs to use longitude and latitude as variables
• markdown - all the HTML elements created from markdown should be reviewed and styled if required. Consider adding the .markdown class to any elements in the site that are run through Hugo's markdownify function
• metrics - This block should be updated to show more metrics (as on the old website), the front matter template needs boolean fields to show/hide each available metric, and we need to determine the best way to update the data that it pulls in (so far it's using json stored in the data directory)
• paginator - This block is used for list pages (the News, Webinars, Jobs pages). It needs to be tested and styled