Two factor authentication plugin using YubiKey

With this plugin you can use a YubiKey hardware token device (available from Yubico.com) for two-factor authentication in Joomla!. The OTP validation is performed against the YubiCloud servers.
SQL files for the YubiKey two factor auth plugin
Changed description of plg_twofactorauth_yubikey for greater clarity
Merge branch 'refs/heads/projects-master' into feature-twofactor-yubikey
Merge branch 'refs/heads/projects-master' into feature-twofactor-yubikey

Conflicts:
	administrator/components/com_admin/sql/updates/mysql/3.2.0.sql
	administrator/components/com_admin/sql/updates/postgresql/3.2.0.sql
Improved YubiKey handling

- Error message shown when you try to activate this feature but the OTP is invalid or doesn't validate against YubiCloud's servers
- Shuffle the list of YubiCloud servers, using a different, random one every time (helps spread out the load and improve the resilience of the implementation)
- Use a time based nonce instead of the form token to prevent YubiCloud responding with REPLAYED_OTP if the form token doesn't change between subsequent attempts
The YubiKey authentication would always return false
 # [#32310] Regression: Restore lost editor configuration tab. 
(Fix #2292)
 # [#32393] /layouts not included in robots.txt  Thanks Matt Thomas
(Fix #2306)
 # [#32378] Installation error: JLIB_DATABASE_QUERY_FAILED. Thanks
Marcel van Beelen
(Fix #2308)
 # [#32394] Replace JLess uses with FOFLess. Thanks Michael Babker
(Fix #2311)
 $ [#31954] Another batch of en-GB grammar corrections  Thanks Brian
Teeman
(Fix #1938)
 # [#32297] Refactoring com_config. Thanks Buddhima Wijeweera
(Fix #2242)
[#32401] *Custom module Options hard to find (Fix #2318)
[#32398] Some older php admin users can't login (Fix #2315)
[#32150] tag added to an article gets removed if ordering changed or in batch processing (Fix #2157)
[#32216] New post install/post update messages (Fix #2186)
[#32330] Removing postinstall_message_id from postinstall INSERT queries (Fix #2264)
[#32395] CS errors found in CMS build (mostly com_config related) (Fix #2303)
[#32343] Regression in Module and Plugin views (Fix #2278)