Merge pull request #725 from FrozenNode/dev

Merging 4.13.0 into master
Merge pull request #726 from FrozenNode/dev

Merging 4.14.0 into master
Merge pull request #729 from FrozenNode/dev

Merging 4.14.1 into master
Merge pull request #740 from FrozenNode/dev

Merging 4.14.2 into master
Merge pull request #755 from FrozenNode/dev

Merging 4.15.0 into master
Check is_callable in addition to method_exists when checking for relationships for compatibility with Ardent's $relationsData method of specifying relationships. (fixes FrozenNode/Laravel-Administrator#748)
Escape table names in subqueries (fixes FrozenNode/Laravel-Administrator#758)