* Fix typos in openconnect.rst
change Cerbort->Certbot
Update first line to reflect that openconnect was introduced in 1.3-rolling (T2036)
* typo in dmvpn.rst
* ipsec.rst justification, minor phrasing changes
* l2tp.rst justification and phrasing changes.
* sstp.rst phrasing, justification changes
* Update ipsec.rst
rephrase for clarity and to avoid possessive plural apostrophe
(cherry picked from commit 873a461bdf972ebd815baf50893700b0a2518213)
Rewritten the L2TP documentation
Added the example 'PPPoE over L2TP' to blueprints
(cherry picked from commit 4dd84a7c4d784229209eeb4b0d72457b094e08ce)
The command to set the vpn interface is changed in the rolling release
which is not modified in many configuration examples, corrected syntax
in all pages where it is mentioned
There were minimal grammatical and spelling mistakes in the files which I
corrected as documentation proof reading.
Also added information about few ipsec vpn parameters.
