Display shipping methods for ALL matching zones on checkout
rename output for css assets

In a production environment, when trying to dump the assets, for some reason if the name of the output is backend.css (same of the layout.html.twig), it is overwritten by this and the blueimp gallery is lost.
In the dev environment that doesn't happen.
Renaming the output to something else fixed it for me.
fix inventory unit orphan removement
Modify _variant.html.twig in order to be able to see images at generated pdf invoices
Merge pull request #1145 from foopang/fix/issue-1145

Not able to select a shipping method where there are both shipping zone and product restricted zone that match user's shipping address
Added parameter 'true' to imagine filter
Adding CONTRIBUTING.md file

Inspired by blog post: http://sylius.org/blog/contributing-guide
Merge pull request #1189 from JRomeoSalazar/pdf-images

Images at PDF format invoice
Merge pull request #1176 from fourlastor/patch-1

rename output for css assets
[SettingsBundle] Reduce code duplication across bundles
Merge pull request #838 from stloyd/feature/settings_duplication

[SettingsBundle] Reduce code duplication across bundles
Synchronize Crowdin translations
Merge pull request #1194 from SyliusBot/feature/sync

Synchronize Crowdin translations
Reduce number of image size filter.
Merge pull request #1177 from kayue/patch/imagine-filter-rename

Rename liip_imagine size filter
Merge pull request #1186 from fullpipe/master

[Core] Fix inventory unit orphan removement