Drop 'dsa' and add 'ed25519' private key support

Update README: dropbearconvert requires OpenSSH keys in PEM format.

Changed installation script to rely on variables, especially the list of
handled private key types, to that it automatically packages expected
private keys, instead of having to explicitely name/package them.

src/install/ssh-cryptsetup

@@ -32,7 +32,7 @@ build() {
     local etc_crypttab="/etc/crypttab"
     local dropbear_authorized_keys="/etc/dropbear/initrd.authorized_keys"
     local sshcs_env="/etc/initcpio/sshcs_env"
-    local dropbear_key_types=( "dss" "rsa" "ecdsa" )
+    local dropbear_key_types=( "rsa" "ecdsa" "ed25519" )
     local dropbear_keyfile_prefix="/etc/dropbear/dropbear_"
     local dropbear_keyfile_suffix="_host_key"
     local openssh_keyfile_prefix="/etc/ssh/ssh_host_"
@@ -79,9 +79,9 @@ build() {
 
     # SSH-related files
     add_file "${dropbear_authorized_keys}" "/root/.ssh/authorized_keys"
-    add_file "/etc/dropbear/dropbear_rsa_host_key"
-    add_file "/etc/dropbear/dropbear_dss_host_key"
-    add_file "/etc/dropbear/dropbear_ecdsa_host_key"
+    for keytype in "${dropbear_key_types[@]}"; do
+        add_file "${dropbear_keyfile_prefix}${keytype}${dropbear_keyfile_suffix}"
+    done
 
     # cryptsetup-related files
     add_file "${etc_crypttab}"
@@ -113,8 +113,8 @@ initrd shell):
    - default (and minimum value): 2 minutes
    - negative value to deactivate
 
-Each SSH server key ('dropbear_rsa_host_key', 'dropbear_dss_host_key' and
-'dropbear_ecdsa_host_key' in '/etc/dropbear' folder) is imported from OpenSSH
+Each SSH server key ('dropbear_rsa_host_key', 'dropbear_ecdsa_host_key' and
+'dropbear_ed25519_host_key' in '/etc/dropbear' folder) is imported from OpenSSH
 if present or generated if missing. Fingerprints are displayed upon building
 the initramfs image.
 EOF