config: Simplify EO API

This is:
 - using a property (but terribly ugly due to the ownership on the
   returned value)
 - removing an unused function

Note: This interface Efl.Config covers only elm_config for now. But it's
very generic and could be used in the future for application specific
configuration.

src/lib/efl/interfaces/efl_config.eo

@@ -2,30 +2,29 @@ interface Efl.Config ()
 {
    [[A generic configuration interface, that holds key-value pairs.]]
    methods {
-      /* FIXME: make this a property -- @own is a problem */
-      config_set {
-      	 [[Set configuration]]
-         params {
-            name: string; [[Configuration option name]]
-            val: const(any_value_ptr); [[Configuration option value]]
+      @property config {
+         [[A generic configuration value, refered to by name.]]
+         get {
+            keys {
+               name: string; [[Configuration option name.]]
+            }
+            values {
+               value: any_value_ptr @owned;
+                  [[The value. It will be empty if it doesn't exist. The caller
+                    must free it after use (using $eina_value_free() in C).]]
+            }
          }
-         return: bool; [[$false in case of error: value type was invalid, the
-                         config can't be changed, config does not exist...]]
-      }
-      config_get @const {
-      	 [[Get configuration]]
-         params {
-            name: string; [[Configuration option name]]
+         set {
+            keys {
+               name: string; [[Configuration option name.]]
+            }
+            values {
+               value: const(any_value_ptr);
+                  [[Configuration option value. May be $null if not found.]]
+            }
+            return: bool; [[$false in case of error: value type was invalid, the
+                            config can't be changed, config does not exist...]]
          }
-         return: any_value_ptr @owned; [[Configuration option value]]
-      }
-      config_list_get @const {
-         [[Returns a list of generic values under a given key.]]
-         params {
-            @in name: string; [[Configuration option name]]
-         }
-         return: iterator<any_value_ptr> @owned; [[
-                 List of configuration option values]]
       }
    }
 }

src/lib/elementary/efl_config_global.eo

@@ -106,8 +106,6 @@ class Efl.Config.Global (Efl.Object, Efl.Config)
       }
    }
    implements {
-      Efl.Config.config_set;
-      Efl.Config.config_get;
-      Efl.Config.config_list_get;
+      Efl.Config.config { get; set; }
    }
 }

src/lib/elementary/elm_config.c

@@ -4639,8 +4639,8 @@ _efl_config_global_efl_config_config_set(Eo *obj EINA_UNUSED, void *_pd EINA_UNU
 }
 
 EOLIAN static Eina_Value *
-_efl_config_global_efl_config_config_get(const Eo *obj EINA_UNUSED, void *_pd EINA_UNUSED,
-                                           const char *name)
+_efl_config_global_efl_config_config_get(Eo *obj EINA_UNUSED, void *_pd EINA_UNUSED,
+                                         const char *name)
 {
    Eina_Value *val = NULL;
 
@@ -4766,15 +4766,6 @@ _efl_config_global_efl_config_config_get(const Eo *obj EINA_UNUSED, void *_pd EI
    return NULL;
 }
 
-EOLIAN static Eina_Iterator *
-_efl_config_global_efl_config_config_list_get(const Eo *obj EINA_UNUSED, void *_pd EINA_UNUSED,
-                                              const char *name)
-{
-   // Not implemented: none of the elm_config functions returns a list of primitive types
-   (void) name;
-   return NULL;
-}
-
 EOLIAN static void
 _efl_config_global_profile_set(Eo *obj EINA_UNUSED, void *_pd EINA_UNUSED, const char *profile)
 {