Containerd/Docker Registry HTTP API V2 support

Since containerd relies on a more complete implementation of the HTTP API V2, an basic implementation was added.

Fix: Accept-Header for containerd

Containerd's Accept-Header did not get destructured to an array, so if multiple mediatypes were set like 'TypeA, TypeB' they couldn't be checked correctly.

Now they get serialized to ["TypeA", TypeB"], which is checked for a supported type by IPDR

Configurable pull-gateway for server

[feat] configurable pull-gateway for server command
Add the flag —ipfs-gateway to the server command

Example:
ipdr server --ipfs-gateway http://127.0.0.1:8080

HTTPS support

This release introduces two path parameters to the server command for a .key and .crt file. If provided, the server is reachable with HTTPS.
This can be useful if only secure docker registries are allowed.

Example: ipdr server --tlsKeyPath path/server.key --tlsCrtPath path/server.crt