ComboSession issue with writing

Follow up with my commit of a year ago, https://github.com/cakephp/docs/commit/23fc03c12c3eea8456e895c2696444e037cdcc56, we realize that there is another issue with the ComboSession. Take for example, if you have a cache server with two nodes, namely node#1 and node#2.

1. Write data to cache. Cache server chosen node#1 - write successful.
2. By definition, if cache writing is successful, then you write the data into database by calling `parent::write`. Since step#1 is successful, no data has been written into the cake_session database yet.
3. This time, app issues a read. Read trying to read data from cache server. Cache server chosen node#2 - read failure. When read fails, it fall back to database reading. Now database do not have such session, so session is lost - user logged out.

To tackle this, we should always write to both cache and database to synchronize database to the cache servers.
[fr] follow #1719
[fr] fix typos
[fr] follow #1717

Update views.rst, deprecation of $title_for_layout
[fr] follow #1535 & #1609

Divide plugins section
[fr] follow #1714

Line length
Merge pull request #1761 from blackpuppy/zh

[en] correct origianl text
Merge pull request #1760 from chaoszcat/patch-6

ComboSession issue with writing
Follow #1760 for other langs
Merge branch 'master' into zh