add pdf file fields
Merge branch 'develop' of https://github.com/alexey-kozlenkov/ExadelPractice into develop
Merge branch 'develop' of https://github.com/alexey-kozlenkov/ExadelPractice into develop
Fix bug with getting unnecessary documents
One more update for documents
add excel file fields; fix student english bug; fix document dao bug
Merge branch 'develop' of https://github.com/alexey-kozlenkov/ExadelPractice into develop
Merge branch 'develop' of https://github.com/alexey-kozlenkov/ExadelPractice into develop

Conflicts:
	src/main/java/com/exadel/studbase/dao/impl/DocumentDAO.java
refactored code
add feedbacks start
Merge branch 'develop' of https://github.com/alexey-kozlenkov/ExadelPractice
Update billable-filter, now works correct.
Merge branch 'develop' of https://github.com/alexey-kozlenkov/ExadelPractice into develop