Merge branch 'feature/native-captcha' into 'develop'

Add native captcha and enable it by default.

Closes #1017 and #1405

See merge request pleroma/pleroma!2060

diff --cc priv/static/static/font/fontello.1576166651574.svg
index f5e497ce4b62296ad5384072a1319f824e1d1851,f5e497ce4b62296ad5384072a1319f824e1d1851..f5e497ce4b62296ad5384072a1319f824e1d1851
mode 100644,100755..100755
--- 1/priv/static/static/font/fontello.1576166651574.svg
--- 2/priv/static/static/font/font/fontello.svg
+++ b/priv/static/static/font/fontello.1576166651574.svg