Support opening password protected PDF files

[esensar]

This closes #712

TODO

• [x] Merge https://github.com/SimpleMobileTools/Simple-Commons/pull/1725 and update ref in build.gradle

[tibbi]

do not close the whole Enter password dialog after inserting an invalid password, just show a toast and clear the password field

[esensar]

do not close the whole Enter password dialog after inserting an invalid password, just show a toast and clear the password field

I have opened up a PR on Simple-Commons, since it is needed to implement that: https://github.com/SimpleMobileTools/Simple-Commons/pull/1725

[tibbi]

looks good now, thanks

[typebrook]

Many thanks! @esensar @tibbi