base: briefideas logo

* Adds logo for journal of brief ideas.
  (closes #64, closes openjournals/brief-ideas#5)

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
base: github logo relationship addition

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
deposit: new related relationships

* Adds new relationships isIdenticalTo, isPartOf, hasPart.
  (closes #38)

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
deposit: WTForms deprecation warning fix

* Fixes WTForms 2.0 deprecation warnings. (addresses #65)

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>