Update INSTALL_ARCHIVE.md
Update and rename UPGRADE-5.2.md to UPGRADE.md
Update UPGRADE.md
Merge pull request #84 from ezsystems/install_upgrade_doc_fixes

Install upgrade doc fixes for 5.2
Update composer to 5.3
EZP-21044: Added OPTIONS routes loading to routing.yml
Merge pull request #86 from ezsystems/fix/EZP-21044-rest_HTTP_OPTIONS

EZP-21044: Added OPTIONS routes loading to routing.yml