Merge branch 'cs/#6130-Zend_-classnames-replacement'

Close #6130
Fix undefined classes in phpDoc
Fix undefined class constant
Fix possible undefined methods in inherited classes
#6094 - changing boolean -> bool as of @samsonasik's suggestion (see #3342)
#6094 - removing unused `null` default property value
Merge branch 'hotfix/#6094-undefined-symbols-fixes' into develop

Close #6094
Forward Port #6094