activitypub: use Activity.normalize() in several places instead of using Activity.get_by_ap_id() directly.

[Pleroma.Web.MastodonAPI.MastodonAPIController]: Add rights to initial_state

See merge request pleroma/pleroma!236

Related to pleroma/mastofe#20

Return empty array from /api/qvitter/mutes.json

See merge request pleroma/pleroma!234

Add more configurability to how blocks work

See merge request pleroma/pleroma!203

config: add application/xml mimetype support.

See merge request pleroma/pleroma!228

Empty 2.4.x endpoints and ``api/v2/search``

See merge request pleroma/pleroma!214

Hnng!

mrf simple: add accept lists

See merge request pleroma/pleroma!231

accept lists supplement reject lists by requiring that any message accepted by contained
by the accept list.

in other words, this functionality can be used to implement instances similar to
awoo.space.

Add streaming to media tabs of federated and local TLs

See merge request pleroma/pleroma!225

fix follow relationship leaks when blocked

See merge request pleroma/pleroma!230

activitypub: support filtering activities by whether or not they are a reply (closes #109)

Closes #109

See merge request !226

handle ActivityStreams 2.0 contentMap

See merge request !229

this is needed for activitypub conformance

ref #213