CRM-21127 - Document fixed return properties in api.Event.get

Adds documentation for https://github.com/civicrm/civicrm-core/pull/10984

Restore alternative options to icons list

Use more consistent capitalization and typography

Document civi-test-run script (take 2)

Add callback example

This opening tag used to be required for syntax highlighting to work
properly in code blocks. Now we no longer need it.

Add `karma` and `upgrade`. Reorder alphabetically.

Replace context descriptions with descriptions from buildOptionsConte…

Update pr-review.md

Update civix.md

Find/replace `(?<=\w) {2,}` with ` `

Remove "editorial" TODO item from "If the PR contains database upgrades".

Update verify-fix.md

Update debugging.md

api/changes - Clean up formatting under "4.7.0: Global $civicrm_setting"

Update planning.md

With only one example, a reader might misinterpret the example as saying
that `Search Preferences` has been renamed `domain`.  Including two examples
should more clearly indicate that *all* group-names are now flattened to
just `domain`.

This section documents two distinct changes, but they had different
formatting -- which made it seem that (perhaps) the one code-block was
describing both changes.

This change uses similar formatting for both examples and changes the
indentation/alignment to indicate that they're distinct.

Update lifecycle.md

Update publish.md

Update advanced.md

Removed extraneous space in **Viewing errors in logfiles**

Update troubleshooting.md

Update structure.md

Update index.md

Update release-process.md

Reading for content; editing for consistency. 
Updated per seamuslee001's comment, and I found another missed edit in the automate testing paragraph.

Reading for content; editing for consistency.

Reading for content; editing for consistency.