Set default to `expanded` for collapsible repo groups.

Move the new property `web.collapsibleRepositoryGroups` into the
`web` section, close to the list type property. Set the default
to be `expanded`, so that the new feature is visible but the list
is still the full list like before.

Add new value `tree` to the description of the property
`web.repositoryListType`.

src/main/distrib/data/defaults.properties

@@ -1263,6 +1263,7 @@ web.allowAppCloneLinks = true
 # Choose how to present the repositories list.
 #   grouped = group nested/subfolder repositories together (no sorting)
 #   flat = flat list of repositories (sorting allowed)
+#   tree = group nested/subfolder repositories in a tree structure with folding branches
 #
 # SINCE 0.5.0
 web.repositoryListType = grouped
@@ -1280,6 +1281,20 @@ web.repositoryRootGroupName = main
 # SINCE 0.8.0
 web.repositoryListSwatches = true
 
+# Specify the behaviour of the Repository groups on the "Repositories"
+# page, specifically whether they can be collapsed and expanded, and
+# their default state on loading the page.
+# Only on repositoryListType grouped 
+#
+# Values (case-insensitive): 
+#   disabled  - Repository groups cannot collapsed; maintains behaviour
+#               from previous versions of GitBlit.
+#   expanded  - On loading the page all repository groups are expanded.
+#   collapsed - On loading the page all repository groups are collapsed.
+#
+# SINCE 1.9.0
+web.collapsibleRepositoryGroups = expanded
+
 # Defines the default commit message renderer.  This can be configured
 # per-repository.
 #
@@ -2154,17 +2169,3 @@ filestore.storageFolder = ${baseFolder}/lfs
 # Common unit suffixes of k, m, or g are supported.
 # SINCE 1.7.0
 filestore.maxUploadSize = -1
-
-# Specify the behaviour of the Repository groups on the "Repositories"
-# page, specifically whether they can be collapsed and expanded, and
-# their default state on loading the page.
-# Only on repositoryListType grouped 
-#
-# Values (case-insensitive): 
-#   disabled - Repository groups cannot collapsed; maintains behaviour
-#              from previous versions of GitBlit.
-#   expanded - On loading the page all repository groups are expanded.
-#   collapsed - On loading the page all repository groups are collapsed.
-#
-# SINCE 1.9.0
-web.collapsibleRepositoryGroups = disabled