feat(media): clean media api + create an entity per media type

app/Database/Migrations/2020-05-29-120000_add_media.php

app/Database/Migrations/2020-05-30-101500_add_podcasts.php

app/Database/Migrations/2020-06-05-170000_add_episodes.php

app/Database/Migrations/2020-12-25-120000_add_persons.php

app/Entities/BaseEntity.php

app/Entities/Episode.php

app/Entities/ImageOLD.php

app/Entities/Media/Audio.php

app/Entities/Media/BaseMedia.php

app/Entities/Media/Chapters.php

app/Entities/Media/Document.php

app/Entities/Media/Image.php

app/Entities/Media/Transcript.php

app/Entities/Media/Video.php

app/Entities/MediaOLD.php

app/Entities/Person.php

app/Entities/Podcast.php

app/Helpers/rss_helper.php

app/Helpers/seo_helper.php

app/Libraries/MediaClipper/VideoClip.php