Merge pull request #187 from gregquat/2.1

Updating 2.1 from sf-docs
Merge pull request #188 from gregquat/2.1

Merge pull request #181 from martinqt/translate_images
Fix typo (see PR #189)
Grammar typo (see #191)
Add sentence for french contributors
Merge pull request #192 from greg0ire/contributing_to_the_french_documentation

Add sentence for french contributors
Fixing typos
add missing backtick
What is meant here is the SCM repository (git, svn)
Merge pull request #194 from greg0ire/bundles_best_practices

Bundles best practices
replacing 'dans' by 'sur'
maj from sf-docs 02/11 to 05/11
maj 05/11 -> 09/11 + twig_reference.rst (up to date)