Update archetypes for activities & sections

archetypes/activity/index.md

++++
+title = "{{ .Name | humanize | title }}"
+date = "{{ .Date }}"
+weight = 10
++++

archetypes/docs.md

----
-title: "{{ .Name | humanize | title }}"
-weight: 1
-# bookFlatSection: false
-# bookToc: true
-# bookHidden: false
-# bookCollapseSection: false
-# bookComments: false
-# bookSearchExclude: false
----

archetypes/posts.md

----
-title: "{{ .Name | humanize | title }}"
-date: {{ .Date }}
-# bookComments: false
-# bookSearchExclude: false
----

archetypes/section/_index.md

++++
+title = "{{ .Name | humanize | title }}"
+weight = 10
+bookCollapseSection = true
++++
+
+{{< section >}}