Update configuring_taxation.rst

Hello
Maybe this is as typo at 18th line:
.tax_manager instead of .tax_category?
little service fix
Remove Corebundle price attribute from product_builder.rst
warn about an existing implementation in CoreBundle
fix sylius_settings_get
Cookbook how to extend the menus
Update configuration.rst

* Add promotion_subject classes
* Add missing validation groups
Merge pull request #135 from abimus/feature/extending-menu

Cookbook how to extend the menus
Merge pull request #136 from marcaube/patch-1

[PromotionsBundle] Update configuration.rst
Update prototypes.rst

Correct name service 'sylius.builder.prototype'
Merge pull request #138 from pvvsecl/patch-1

Error prototypes.rst
Merge pull request #111 from tuchk4/patch-1

Update configuring_taxation.rst
Merge pull request #113 from diimpp/patch-2

Remove Corebundle price attribute from product_builder.rst
Language changes

Small language changes, but they make this page a pleasure to read. Keep up the good work!
Merge pull request #139 from timon-schroeter/patch-1

Language changes
Update installation.rst

typo & little fixes
Merge pull request #141 from erheme318/patch-2

Update installation.rst
Adding the configuration section
Remove all version suggestions from composer installation docs
Fixed some invalid links
Merge pull request #140 from Sylius/resource-bundle

Adding the configuration section