metadata: small update, propose required

see ElektraInitiative#1588

doc/METADATA.ini

@@ -241,6 +241,15 @@ status= implemented
 usedby/tool= gen
 
 [rationale]
+status= idea
+description= Information why this configuration setting exists
+	and in which scenarios it should be considered to be removed
+
+[requirement]
+status= idea
+description= Information based on which requirement the configuration
+	setting exists. Gives hints when to reevaluate the configuration
+	setting.
 
 [description]
 description = this is information provided from the developer/maintainer
@@ -325,17 +334,25 @@ description = checks if the subkeys form a valid array and are not smaller/large
 	than as given.
 example = 4-20
 
+[require]
+type = boolean
+status = proposed
+description = Alternative to "default": ensures that an application
+	will be able to successfully retrieve a configuration setting.
+
 [required]
 type = range
-status= implemented
+usedby/plugin = required
+status = unclear
 description = for _ as basename as array. Otherwise the presence determines
 	if a key is required.
+	In process of being replaced in favour of require.
 
 [mandatory]
-type = range
-status= unclear
-usedby/plugin= required
-description = alternative for required plugin
+type = boolean
+usedby/plugin = required
+status = unclear
+description = In process of being replaced in favour of require.
 
 #
 # Per-Key Log
@@ -658,6 +675,11 @@ description= evaluate expression to check if key should be included, program sho
 	abort or however evaluate plugin is configured
 
 
+[accessibility]
+status= idea
+description= who is allowed to edit this configuration setting?
+
+
 
 #
 # Old stuff inherited from filesys plugin