Deprecate Macro.expand_all

Eventually we would like to introduce expand_all with
proper compiler expansion semantics.
Update CHANGELOG
Ensure `defexception` fields can be set dynamically

Closes #1751
Ensure cover compiling results yield the app name

Closes #1743
Ensure we raise a meaningful error when there is no SCM

Closes #1742
Update code comment
Get rid of @only in List.Chars, improve deprecation message
Assert messages are received instead of flushing.

Since at the moment we call flush there is no guarantee
we received all desired messages.
First pass at formatting iex help output
Fix up handling of enabled: color option
Allow H3s to be nested inside lists
respond to review. make internal methods private. Add tests for external methods.
Split IEx colors into categories
mend
add a few extra tests
fix bug with nested lists
fix problem with lone stars
Improve coverage of backticks, underscsores, etc in ANSIDocs
Simplify list handling by delegating to the same text handling function
Do not split words for handling inline code