Provide HCaptcha for plone.app.discussion

[ksuess]

… if plone.formwidget.hcaptcha is installed

[ksuess]

Implemented with

• https://github.com/plone/plone.app.discussion/pull/232 for latest version (4.x)
• https://github.com/plone/plone.app.discussion/pull/229 for version 3.4.x for Plone 5.2

[ksuess]

Can we get releases for 3.4.x and 4.x please, @mauritsvanrees, thank you.

[mauritsvanrees]

@ksuess Thanks for your work! I have released 3.4.8 and 4.1.0.