Move docs about project state to "config-project-config.txt"

We have two documents, e.g. "config-project-config.txt" and
"project-configuration.txt", containing doc for project
configs. "config-project-config.txt" intends to document
avaliable configs to the project through "project.config",
"rules.pl" and "groups" file. "project.configuration" intends
to document the configs avaliable through the UI. However,
both of them are not complete, making it hard for users to
learn how to config their projects.

This commit and followup commits proposes to move docs
about "Project Options" in "project-configuration.txt" to
"config-project-config.txt" and then just referencing them
from "project-configuration.txt". Hopefully, this could
make it easier for users to understand Gerrit project configs.

Change-Id: I0cf5013bd5260cf69cdb6e8ec51608cfc1d59d79
diff --git a/Documentation/config-project-config.txt b/Documentation/config-project-config.txt
index 4456484..a84077b 100644
--- a/Documentation/config-project-config.txt
+++ b/Documentation/config-project-config.txt
@@ -96,7 +96,41 @@
 
 These are the keys:
 
-- Description
+[[description]]description::
++
+A description for the project.
+
+[[state]]state:
++
+This setting defines the state of the project. A project can have the
+following states:
+
+- `Active`:
++
+The project is active and users can see and modify the project according
+to their access rights on the project.
+
+- `Read Only`:
++
+The project is read only and all modifying operations on it are
+disabled. E.g. this means that pushing to this project fails for all
+users even if they have push permissions assigned on it.
++
+Setting a project to this state is an easy way to temporary close a
+project, as you can keep all write access rights in place and they will
+become active again as soon as the project state is set back to
+`Active`.
++
+This state also makes sense if a project was moved to another location.
+In this case all new development should happen in the new project and
+you want to prevent that somebody accidentally works on the old
+project, while keeping the old project around for old references.
+
+- `Hidden`:
++
+The project is hidden and only visible to project owners. Other users
+are not able to see the project even if they have read permissions
+granted on the project.
 
 
 [[receive-section]]
diff --git a/Documentation/project-configuration.txt b/Documentation/project-configuration.txt
index f76b5e4..3ed3fdd 100644
--- a/Documentation/project-configuration.txt
+++ b/Documentation/project-configuration.txt
@@ -143,35 +143,8 @@
 [[project-state]]
 === State
 
-This setting defines the state of the project. A project can have the
-following states:
+See details at link:config-project-config.html#project-section[project section].
 
-- `Active`:
-+
-The project is active and users can see and modify the project according
-to their access rights on the project.
-
-- `Read Only`:
-+
-The project is read only and all modifying operations on it are
-disabled. E.g. this means that pushing to this project fails for all
-users even if they have push permissions assigned on it.
-+
-Setting a project to this state is an easy way to temporary close a
-project, as you can keep all write access rights in place and they will
-become active again as soon as the project state is set back to
-`Active`.
-+
-This state also makes sense if a project was moved to another location.
-In this case all new development should happen in the new project and
-you want to prevent that somebody accidentally works on the old
-project, while keeping the old project around for old references.
-
-- `Hidden`:
-+
-The project is hidden and only visible to project owners. Other users
-are not able to see the project even if they have read permissions
-granted on the project.
 
 === Use target branch when determining new changes to open