Add documentation for LCP echo ONC property

Add documentation for LCP echo ONC property

Add documentation for the "LcpEchoDisabled" ONC property.

BUG=463602
TEST=None

Committed: https://crrev.com/9be8c5d50aa3c09504d6d0312cca24376aeb1ace
Cr-Commit-Position: refs/heads/master@{#324256}

[Paul Stewart, 2015-04-07 15:35:04]

pstew@chromium.org changed reviewers:
+ pneubeck@chromium.org, stevenjb@chromium.org

[pneubeck (no reviews), 2015-04-08 08:22:31]

thanks!
lgtm

https://codereview.chromium.org/1060333003/diff/1/components/onc/docs/onc_spe...
File components/onc/docs/onc_spec.html (right):

https://codereview.chromium.org/1060333003/diff/1/components/onc/docs/onc_spe...
components/onc/docs/onc_spec.html:1038: (optional)
nit: 
(optional)
->
(optional, defaults to <span class="value">false</span>)

https://codereview.chromium.org/1060333003/diff/1/components/onc/docs/onc_spe...
components/onc/docs/onc_spec.html:1039: <span class="type">bool</span>
bool -> boolean

[Paul Stewart, 2015-04-08 17:36:54]

The CQ bit was checked by pstew@chromium.org

[Paul Stewart, 2015-04-08 17:36:54]

The patchset sent to the CQ was uploaded after l-g-t-m from
pneubeck@chromium.org
Link to the patchset: https://codereview.chromium.org/1060333003/#ps20001
(title: "Address pneubeck@'s nits.")

[commit-bot: I haz the power, 2015-04-08 17:37:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1060333003/20001

[commit-bot: I haz the power, 2015-04-08 18:35:53]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-08 18:37:23]

Patchset 2 (id:??) landed as
https://crrev.com/9be8c5d50aa3c09504d6d0312cca24376aeb1ace
Cr-Commit-Position: refs/heads/master@{#324256}