Update plugins.rst

The psr-4 autoload paths should be relative, not absolute.
[fr] follow #1476

Add info about $confirmMessage arg removal.
[fr] follow #1478

Update the 'idField' and 'valueField' options
[fr] follow faf034b

Fixing syntax errors in examples
Merge pull request #1508 from oldskool/patch-4

Update plugins.rst
Remove references about Acl in configurations
Merge pull request #1510 from cakephp-fr/3.0

Remove references about Acl in configurations
Delete cache.rst

CacheHelper has been removed in 6441e418dde28e263890923358882be8eb2ae159
cakephp/cakephp@6441e41

remove cacheHelper link
Merge pull request #1511 from antograssiot/3.0

CacheHelper reference removal
add removal of CakeHelper in migration guide

related to cakephp/cakephp@6441e41
add detail on future plugin
fix typo
Add reasoning for cachehelper removal.
Update TOC.
Removed not needed 'to' in ORM migration and changed 'object' to 'objects' in ORM
Removed not needed 'to' in ORM migration and changed 'object' to 'objects' in ORM
Merge branch '3.0' of github.com:amitrb/docs into 3.0
Merge pull request #1515 from amitrb/3.0

Removed not needed 'to' in ORM migration and changed 'object' to 'objects' in ORM
Fixed minor typos for ORM's query builder