links.md: lesson-specific links

Signed-off-by: Maxim Belkin <maxim.belkin@gmail.com>

Pull Request: carpentries/styles#374

aio.md: fix indentation and variable declaration

ISSUE_TEMPLATE.md: Nudge contributors to specify episodes unambigously

See https://github.com/swcarpentry/r-novice-inflammation/issues/401 > 3.

Fix https://github.com/carpentries/workshop-template/issues/540

See apple.com/macos

Code/callout/prereq/etc blocks: set left and right margins to 0

* replace page.root with 'base' variable that knows path level

* deal with case of trailing / in URL

* use link to figure out path for logos

* simplify path building for favicons

* baseurl isn't used in our template so it can removed
* use 'base' variable for path root instead of unecessary http request to
  site.url

* replace page.root with 'base' variable that knows path level

* deal with case of trailing / in URL

* use link to figure out path for logos

* simplify path building for favicons

* baseurl isn't used in our template so it can removed
* use 'base' variable for path root instead of unecessary http request to
  site.url

* rename variable, consolidate comments

* rename variable in template files