Ignore invalid env for SSH Server (OSX fix)

- #2153 remove require for gravatar

Minor typo in en-US locale: gloabl -> global

Fix postinstall to use GOGS_CUSTOM instead of symlinking

Reword messages for PR auto merging (#2117)

LOCAL_ROOT_URL for workers accessing web service

The reasoning for that is in the previous commit.

Local (DMZ) URL for gogs workers (such as ssh update) accessing web service. In
most cases you do not need to change default http://localhost:HTTP_PORT/. You
may need to alter it only if your ssh server node is not the same as http node,
eg. running behind proxy on different node than web server.

                     --- 80 public port -> 8080 -- web server node
                    /
    public proxy --<
                    \
                     --- 22 public port -> 10022 -- ssh server node

This option is not intended to be accessible via web GUI settings, since it is
unlikely someone needs to change it to somethings else than default
http://localhost:HTTP_PORT/ which should work for most of the cases.

But this should land into the documentation somewhere.

fixup