[DS-2112] fix NPE if org.dspace.app.mediafilter.MediaFilterManager.processBitstream is undefined

Also take a few IDE hints to tidy up the region.
DS-2135 changed the import url for bootstrap in _main.scss
Merge pull request #631 from atmire/DS-2135

DS-2135 changed the import url for bootstrap in _main.scss
Merge pull request #617 from mwoodiupui/DS-2112

[DS-2112] fix NPE if filter.org.dspace.app.mediafilter.publicPermission is undefined