Capitalize L and add missing 'layer' word
Fix up mistakes in REST and ConnectionManager docs.

Fixes #1829
Update docs for cakephp/cakephp#4811
Merge pull request #1830 from cakephp/issue-1829

Fix up mistakes in REST and ConnectionManager docs.
Update for Inflector::slug() default replacment change.
Merge pull request #1793 from cakephp/3.0-inflector-slug

Update for Inflector::slug() default replacment change.