Update docs for weak password hashing.

Refs cakephp/cakephp#5346
Update usage examples also mention themes
Refer to creating a bake theme

Since the usage section now points out what the theme option is for

Also attempt to correct the list rendering.
another badly rendered list
consistent prompt
Correct bake syntax list
Merge pull request #2093 from AD7six/3.0-bake

3.0 bake
Fix typo.
Fix example for adding detector using a callable.
Merge pull request #2091 from cakephp/weak-password-salt

Update docs for weak password hashing.
Merge pull request #2094 from ADmad/3.0

Fix example for adding detector using a callable.