0.14.0 release

• update XCode images 11 -> 11.2
• add Clang 9 builds
• fetch up to 600 repositories from the GitHub api for the remote feature
• update Linux host image Xenial -> Bionic
• remove Clang 7 workaround; use conanio/clang70 container for new jobs
• remove check for existing readme in the checks features
• delete Bincrafters and Conan Community author attributes
• remote feature: put CI skip tags in the long commit description
• remove standalone CLI feature to update only the readme
• update check for tools.get() to look if conandata.yml is used
• increase minimum Conan version to 1.18.0 as it is the first version which supports user/channel as optional
• fix jobs_update not returning explicit value, causing the remote feature to not push modified files
• add latest CCI reference updates