feat: console help, examples and named loggers (SummerCMS v0.4.0)

Every command gets long help and examples, descriptions in imperative
sentence case, and a warn-only TestCommandsDocumented over bonfire.CheckDocs.
The plugin logs through a diary component logger instead of the process
default logger. Requires SummerCMS v0.4.0; command names and flags unchanged.

controllers/api/logger.go

@@ -0,0 +1,7 @@
+package api
+
+import "git.golem15.com/golem15/summercms/modules/diary"
+
+// pluginLog is the plugin's logger: its records carry component=menu, so
+// config/log.yaml can raise or lower them (log.components.menu).
+var pluginLog = diary.For("menu")