cli: changing nmcli output to better fit both computer and human needs

The output is basically tabular with fields (columns) presenting specific pieces of info.
Each line represents a single object. It's possible to switch to multiline output using
'--multiline' option. In that mode single object is presented on more lines - each field
on its line.
Terse mode now uses ':' as field separator. It also escapes all occurences of ':' and '\'
inside field values to ease parsing. The escaping behaviour can be controlled through
'--escape' option. By default, escaping is switched on in tabular mode. When using terse
mode ('--terse'), '--fields' option is mandatory for specifying required fields. That helps
for flexibility and backwards compatibility.
Not all output is converted yet.

cli/src/utils.h

@@ -20,8 +20,15 @@
 #ifndef NMC_UTILS_H
 #define NMC_UTILS_H
 
+#include <glib.h>
+
+#include "nmcli.h"
+
+/* === Functions === */
 int matches (const char *cmd, const char *pattern);
 int next_arg (int *argc, char ***argv);
+GArray *parse_output_fields (const char *fields_str, const NmcOutputField fields_array[], GError **error);
+void print_fields (const NmcPrintFields fields, const NmcOutputField field_values[]);
 void print_table_header (const char *name, ...);
 void print_table_line (int indent, ...);