Enforce model aliases when generating order by clauses.

Invalid SQL could be created by sorting on an invalid alias, with
a field that exists on the model.

Fixes #3797
Simplify how fullBase is calculated.

Using FULL_BASE_URL fixes URL generation when URL rewriting is
disabled.

Fixes #3777
Update version number to 2.3.4
Merge branch 'master' into 2.4

Conflicts:
	lib/Cake/VERSION.txt