Update toString() to use late static binding for encoding methods

Change-Id: I470379b8527852d5f36145c88ab05cbb51582103
Merge branch 'hotfix/3948'

Close #3948
Merge pull request #3960 from jvandemo/hotfix/zend-uri-late-static-binding

Update toString() to use late static binding for encoding methods
Merge branch 'hotfix/3960' into develop

Forward port #3960