Update installation.rst

As per https://github.com/Sylius/Sylius/issues/1574#issuecomment-44409941 Replaced the setProduct call to setVariant
Updating the resource component doc.
Small fix and missing stuff.
Updating the configuration reference
Merge pull request #169 from aRn0D/resource/component

Updating the resource component doc.
Merge pull request #180 from aRn0D/resource/config-ref

Updating the configuration reference
Adding summary chapter
Merge pull request #172 from aRn0D/component/summary

Adding summary chapter
Merge pull request #168 from aRn0D/resource/index-resource

Small fix
Minor - Completing example.
Merge pull request #186 from jmontoyaa/patch-2

Minor - Completing example.
Fixed location for sylius models. (From Bundle to Component)
Merge pull request #188 from sivolobov/fix_models_place

Fixed location for sylius models. (From Bundle to Component)
Update models.rst
Merge pull request #192 from allanbrault/patch-1

Update models.rst
Updating the Currency component doc
Merge pull request #191 from aRn0D/currency/component

Updating the Currency component doc
Updating the registry component doc
Creating the summary chapter
Updating the resource bundle doc