Add ubuntu focal support

[fluser]

Basic installation is working now.

Fixed:

• Some problems with previously added php8.0
• Problem with renamed service name under Ubuntu Focal (bind9 -> named)
• Problem with libssl guessing in Dovecot
  • libdovecot-login.so does not provide any information about libssl -> Workarround with libdcrypt_openssl.so
  • Seems to work fine with my tested distributions (Debian Buster / Stretch and Ubuntu Focal)

Added:

• Vagrant for Ubuntu 20.04

[fluser]

May conflict with #101 because of re-added PHP8.0 in package lists

[fluser]

Vagrant is working fine with dev composer packages.

git diff
diff --git a/Vagrant/scripts/provision_imscp.sh b/Vagrant/scripts/provision_imscp.sh
index 2e2daace5..90991aaf2 100644
--- a/Vagrant/scripts/provision_imscp.sh
+++ b/Vagrant/scripts/provision_imscp.sh
@@ -29,4 +29,5 @@ __END__
 EOT
 
 # Execute the i-MSCP installer using preseeding file
+export IMSCP_PKG_DEVELOPMENT=TRUE
 perl /usr/local/src/imscp/imscp-autoinstall --debug --verbose --preseed /tmp/preseed.pl

Needed as workarround for:

    imscp_ubuntu_focal: [DEBUG] iMSCP::LockFile::release: Releasing exclusive lock on /var/lock/imscp-backup-imscp.lock
    imscp_ubuntu_focal: [ERROR] Package::WebmailClients::Roundcube::Handler::preinstall: Couldn't install Roundcube Javascript dependencies: ERROR: Incorrect sha1 sum of /var/www/imscp/gui/vendor/imscp/roundcube/roundcubemail/temp/js_cache/jstz-1.0.6.js. Expected: 4291cd3b259d2060460c2a6ab99f428d3c0c9537, got: e480a05703878a2889d0ee5b67aeda52e8e7b7b1 at /var/www/imscp/engine/PerlLib/Package/WebmailClients/Roundcube/Handler.pm line 138.
    imscp_ubuntu_focal: 
    imscp_ubuntu_focal: [ERROR] autoinstaller::Adapter::DebianAdapter::install: An error occurred while the installation steps.