SECURITY: Do checks on all upload types

Also, verify file before stashing it

Based on change Ib2474cb778d53959a4f479e53d0392f916b18d83

Change-Id: I2b230af2f23c4303acdb695468608df19a88d16d
Updated release notes and version number

Change-Id: I1fb122b2e946df330578474ace5c1da7e163f5b1
Merge branch 'REL1_19' of https://gerrit.wikimedia.org/r/p/mediawiki/core into REL1_19