Added tests for `confirm_email` action.

unless requested by admin or moderator.

for registration, authentication, email confirmation, confirmation resending.
Made admin methods create confirmed users.

Introduced User.register/1 to encapsulate User record creation and post-registration actions.

[#114] Account confirmation email, registration as unconfirmed (config-based), auth prevention for unconfirmed.

Instance/Runtime static plug

See merge request !567

This allows to set-up an arbitrary directory which overrides most of the
static files: index.html static/ emoji/ packs/ sounds/ images/ instance/
favicon.png.

If the files are not present in the directory, the bundled ones in
priv/static will be used.

2018 12 17 update frontend

See merge request !565

Fix uploads test.

See merge request !564

Fix update_profile failing due to OAuth token record in assigns instead of string

Closes #459

See merge request !561

[#449] fix text field

See merge request !563

Captcha

See merge request !550

Fix tagging problems for existing instances.

See merge request !562

Add tests for Mix tasks

See merge request !555

Upgrade to Phoenix 1.4

Closes #451

See merge request !560

WebFinger: Sends a 400 when resource param is missing, fix XRD typo in test

See merge request !554