Upgrade to Bouncy Castle 1.50

Release notes:

https://www.bouncycastle.org/releasenotes.html
Merge pull request #952 from andrewgaul/bouncy-castle-1.50

Upgrade to Bouncy Castle 1.50
2.0 release notes.
[maven-release-plugin] prepare release parent-2.0.0
[maven-release-plugin] prepare for next development iteration
Unindent the website samples.
Merge pull request #953 from square/jw/unindent

Unindent the website samples.
Merge branch 'okhttp_20'

* okhttp_20:
  [maven-release-plugin] prepare for next development iteration
  [maven-release-plugin] prepare release parent-2.0.0
Merge remote-tracking branch 'origin/master' into friendly_form_building
escape the name and filename tokens

This behavior matches Chrome, but not Firefox, and I highly advise
against relying on it.