bug fix: epedev-342, epedev-364

change credit & field field to required in edit epe_dbfile custom form
change resource browser thumbnail image style to scale & crop
remove views pager from image source view

this change is for epedev-354 which is not yet complete
bug fix epedev-342

fix LLB embedded resource not having credit & source url field error
message
Merge pull request #2 from ooiepe/3.2-bug-fixes-ay

3.2 bug fixes ay