GUACAMOLE-470: Restore ENUM "color-scheme" parameter for SSH and Telnet.

This reverts commit 4e610f2d1b.

guacamole-ext/src/main/resources/org/apache/guacamole/protocols/ssh.json

@@ -43,7 +43,8 @@
             "fields" : [
                 {
                     "name"  : "color-scheme",
-                    "type"  : "TEXT"
+                    "type"  : "ENUM",
+                    "options" : [ "", "black-white", "gray-black", "green-black", "white-black" ]
                 },
                 {
                     "name"  : "font-name",

guacamole-ext/src/main/resources/org/apache/guacamole/protocols/telnet.json

@@ -39,7 +39,8 @@
             "fields" : [
                 {
                     "name"  : "color-scheme",
-                    "type"  : "TEXT"
+                    "type"  : "ENUM",
+                    "options" : [ "", "black-white", "gray-black", "green-black", "white-black" ]
                 },
                 {
                     "name"  : "font-name",