Added missing xml configuration examples for validation constraints
Adding documentation for the CardScheme validation.
Changed installation chapter

- Added a link to Packagist
- Removed PEAR link
Merge pull request #2069 from WouterJ/patch-30

[Component][Filesystem] Changed installation chapter
Merge pull request #2053 from l3l0/add-some-more-missing-xml-constraints-reference

[Reference][Constraints]Added missing xml configuration examples for validation constraints
[#2053] Backporting XML changes that were applied to 2.1 - thanks to @l3l0
Merge branch '2.0' into 2.1

Conflicts:
	reference/constraints/All.rst
	reference/constraints/Country.rst
	reference/constraints/Date.rst
	reference/constraints/Ip.rst
	reference/constraints/Language.rst
	reference/constraints/Locale.rst
	reference/constraints/Time.rst
	reference/constraints/Type.rst
	reference/constraints/Url.rst
Fixed formatting issue

It seems like ``|`` doesn't get rendered, but `` | `` does.
Merge pull request #2070 from WouterJ/patch-31

Fixed formatting issue
Syntax fix
Merge pull request #2073 from drak/patch-9

Syntax fix
Minor changes on the CardScheme validator
fixed CS
Merge pull request #2054 from Sgoettschkes/issue2023

Adding documentation for the CardScheme validation.
Merge branch '2.0' into 2.1
[#2054] Slight tweaks to new CardScheme document
Merge branch '2.1'
[#2071] Fixing syntax error
Merge branch '2.0' into 2.1
[#2007] Fixing bad versionadded number - thanks to @trompette