Issue #2895581 by chr.fritsch, Wim Leers: Add test coverage ensuring that the media source field cannot be removed from a media type

Issue #2894270 by xjm, seanB, chr.fritsch, Wim Leers: Users unable to add an extension to the file upload field

Issue #2863431 by Manuel Garcia, seanB, naveenvalecha, Gábor Hojtsy, Berdir, tstoeckler, timmillwood, tacituseu, marcoscano: Change "Save and keep un-/published" buttons for media module

Issue #2885486 by seanB, timmillwood, tstoeckler, Wim Leers: Media entity is revisionable but doesn't have a revision link template

Issue #2887269 by Manuel Garcia, phenaproxima, larowlan, xjm: Remove unnecessary prefixing from media libraries

SA-CORE-2017-003 by Berdir, David_Rothstein, Wim Leers, alexpott, catch, cilefen, larowlan, mlhess, pwolanin, quicksketch, samuel.mortenson, smaz, stefan.r, xjm

Issue #2831937 by mtodor, seanB, Wim Leers, phenaproxima, l0ke, webflo, tedbow, Gábor Hojtsy, slashrsm, naveenvalecha, mondrake, oriol_e9g, dawehner, vijaycs85: Add "Image" MediaSource plugin

Issue #2831936 by marcoscano, seanB, chr.fritsch, l0ke, Wim Leers, vijaycs85, phenaproxima, pguillard, johndevman, drubb: Add "File" MediaSource plugin

Issue #2832574 by marcoscano, dawehner, hansfn: Grant "view media" permission by default to all users

Issue #2831274 by slashrsm, seanB, Wim Leers, chr.fritsch, phenaproxima, naveenvalecha, marcoscano, webflo, Gábor Hojtsy, amateescu, Boobaa, iMiksu, mtodor, effulgentsia, xjm, Berdir, tim.plunkett, dawehner, tkoleary, tstoeckler, tedbow, alexpott, yoroy, catch, Bojhan, andypost, jhedstrom, jibran, aspilicious, boztek, cbr, bigbaldy, alex0412, dagmar, blueminds, ekes, Dave Reid, Sam152, bojanz, pixelmord, jonathanshaw, CTaPByK, webchick, samuel.mortenson, dbt102, dishabhadra, proweb.ua, rakesh.gectcr, rasikap, paranojik, pameeela, neardark, NormySan, Primsi, nicolas.rafaelli, romainj, royal121, vladan.me, vpeltot, woprrr, vilepickle, toni04, scheban, tduong, temkin, tim-e, mbovan, mashermike, felribeiro, giancarlosotelo, hctom, euphoric_mv, eric.duran7@gmail.com, edurenye, eelkeblok, H1ghlander, Jaesin, hkirsman, ja_ca, NickWilde, joachim, joshi.rohit100, marcingy, NerOcrO, Mixologic, jcisio, jfrederick, Lukas von Blarer, Maouna: Bring Media entity module to core as Media module