Bring epub and PDF chapter order in sync

At least the first three:
1. getting-started
2. installation
3. cakephp-overview
Merge pull request #2073 from cakephp/2.x-epub-pdf-chapter-order

Bring epub and PDF chapter order in sync
[zh_CN] done /zh/development/sessions.rst
[zh_CN] done /zh/plugins.rst
update deprecated example
Revert b4800b021e18f83f3e73f9f279c6ee53af9129e4 as it breaks the build process.
Merge pull request #2077 from blackpuppy/zh

[zh_CN] done /zh/development/sessions.rst and /zh/plugins.rst