Revert "Fixes #5090: Possible to register js as shimmed AMD module"

This reverts commit 4dcaf3889c1800ea879db1606f7883a21edf3a6f.

Conflicts:
	engine/classes/Elgg/AmdConfig.php
	engine/tests/phpunit/Elgg/Amd/ConfigTest.php
fix(js): Separated elgg_load_js() and elgg_define_js().

Refs #6603, #6497, #5090.
docs(amd): Separated design and guides for AMD docs.

Refs #6603, #6497, #5090.