Testing dependency fixes, Netconf XML declaration and filter logic fix

Install libnghttp2-devel in ubuntu and centos per required dependencies
Ignore case when checking XML declaration encoding value per W3C recommendations
Fix filter logic to follow RFC6241 (7.1, 7.7) and default to subtree

lib/src/clixon_xml_parse.y

@@ -65,6 +65,7 @@
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
+#include <strings.h>
 #include <errno.h>
 #include <stdlib.h>
 
@@ -196,7 +197,7 @@ static int
 xml_parse_encoding(clixon_xml_yacc *xy,
 		   char            *enc)
 {
-    if(strcmp(enc, "UTF-8")){
+    if(strcasecmp(enc, "UTF-8")){
 	clicon_err(OE_XML, XMLPARSE_ERRNO, "Unsupported XML encoding: %s expected UTF-8", enc);
 	free(enc);
 	return -1;