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.
Moving the products models to the component doc
Adding summary chapter, the configuration reference has been updated
Removing working examples
Replace LiipCacheBundle see #1276
replace routing pattern with path
Correct the interface name for attribute subjects

Additionally, improve the description.
Merge pull request #179 from adamelso/patch-1

Correct the interface name for attribute subjects
Merge pull request #178 from jrobeson/replace-routing-pattern-with-path

replace routing pattern with path in all docs
Merge pull request #177 from jmontoyaa/patch-1

Replace LiipCacheBundle with DoctrineCacheBundle
Merge pull request #176 from aRn0D/cart/summary

Removing working examples
Merge pull request #175 from aRn0D/product/summary

Adding summary chapter, the configuration reference has been updated
Merge pull request #174 from aRn0D/product/model

Moving the products models to the component doc
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