Fix for typo in `corctl` and polishing GUI content.

Also updated git_refs after rewrite of openolt history to remove large
binary

Add deprecation notes regarding legacy gitbook toolchain, as links are
broken (cherry pick from fa9389b222cfcb25cb78d7b637ce035a6f82f89f).

Update docs to point to new Trellis documentation (cherry pick from
868f69d87978e171225d17f001b256b5f87e5973)

Change-Id: I90ccdaf8892e51c65fc14e7fd9495537db00b258
(cherry picked from commit 95eade026923f36642586c350a47823c4e483f60)
diff --git a/git_refs b/git_refs
index d5e5e06..b3fec33 100644
--- a/git_refs
+++ b/git_refs
@@ -21,7 +21,7 @@
 kubernetes-service    /docs    3ea0a9c663059b3d8d5cb6609254a05f7fe72219
 olt-service           /docs    b9d725d7d46ed63f63d7cc7d32e149c0ed26a1c6
 onos-service          /docs    32b165a35c8a2779827d91269be5dbac8f3e0cea
-openolt               /        27939d8ed643293fd9f3a7ff4db95d9c0a972aed
+openolt               /        a4d6ba4eaa8d88760cfcd367921c91418b098b35
 openstack             /docs    f1897e0b6b0bb32dc6bc71ccbe21d87190359100
 rcord                 /docs    cd109155ec4d3172fb3d951a6e5c8dbc342e8885
 simpleexampleservice  /docs    ea2919f720a36f60aef284944db06725da503951