D14655: Reimplement signature form field and related utility classes in poppler generator

[Chinmoy Ranjan Pradhan]

chinmoyr added a dependent revision: D14656: #Add utitlity functions for use in 
gui components

#Summary: 

#Test Plan: 

#Reviewers: aacid

#Subscribers: 

Add utitlity functions for use in digital signature verification.

REPOSITORY
  R223 Okular

REVISION DETAIL
  https://phabricator.kde.org/D14655

To: chinmoyr, aacid
Cc: okular-devel, ngraham, aacid