[welcome] Document welcome.conf

- explain requirements keys
 - document show-buttons keys

src/modules/welcome/welcome.conf

@@ -1,18 +1,37 @@
+# Configuration for the welcome module. The welcome page
+# displays some information from the branding file.
+# Which parts it displays can be configured through
+# the show* variables.
+#
+# In addition to displaying the welcome page, this module
+# can check requirements for installation.
 ---
+# Display settings for various buttons on the welcome page.
 showSupportUrl:         true
 showKnownIssuesUrl:     true
 showReleaseNotesUrl:    true
 
+# Requirements checking. These are general, generic, things
+# that are checked. They may not match with the actual requirements
+# imposed by other modules in the system.
 requirements:
+    # Amount of available disk, in GB. Floating-point is allowed here.
+    # Note that this does not account for *usable* disk, so it is possible
+    # to pass this requirement, yet have no space to install to.
     requiredStorage:    5.5
+
+    # Amount of available RAM, in GB. Floating-point is allowed here.
     requiredRam:        1.0
+
+    # To check for internet connectivity, Calamares does a HTTP GET
+    # on this URL; on success (e.g. HTTP code 200) internet is OK.
     internetCheckUrl:   http://google.com
 
     # List conditions to check. Each listed condition will be
     # probed in some way, and yields true or false according to
     # the host system satisfying the condition.
     #
-    # This sample file lists all the conditions that are know.
+    # This sample file lists all the conditions that are known.
     check:
         - storage
         - ram
@@ -20,7 +39,7 @@ requirements:
         - internet
         - root
         - screen
-    # List conditions that must be satisfied (from the list
+    # List conditions that **must** be satisfied (from the list
     # of conditions, above) for installation to proceed.
     # If any of these conditions are not met, the user cannot
     # continue past the welcome page.