Unit tests: cleaned up outdated / unused / commented out code.
Remove dead code
Fixed broken code block in documentation
Reverted incorrect typo fix -_-
Added $isIdentifierColumn documentation

I've added the documentation of the argument $isIdentifierColumn since in case of foreign composite keys it doesn't 
Added 'contains' comparison
Added composer.lock to .gitignore
[BUGFIX] Correct link to Functions, Operators, Aggregates

This fixes the in-page link to the Functions, Operators, Aggregates
section.
Mention flush cannot be called inside postFlush
[DDC-2282] Fix pagination problem with SQL Server.

ORDER BY removed from all count queries when on SQL Server
Fixed SQLServer ORDER BY problem in paginator CountOutputWalker
Added test to check query with ORDER BY and SQLServerPlatform
Merge branch 'GH-572'
Merge pull request #610 from afoeder/patch-1

[BUGFIX] Correct link to Functions, Operators, Aggregates
Don't add empty expression to another one
Merge pull request #602 from alex88/patch-1

Added $isIdentifierColumn documentation
Merge pull request #595 from mnapoli/patch-1

Fixed broken code block in documentation
Merge pull request #601 from jankramer/add-contains-comparison

Add 'contains' comparison
Merge pull request #591 from Aitboudad/master

Remove dead code
[DDC-2304] accept more than 2 parameters in CONCAT function

- Tested and parser validates at least 2 parameters given
- test added for CONCAT function and indentation fixed
- calling getConcatExpression using call_user_func_array as number of arguments is not known removing dependency to patch DBAL
- maintaining backward compatibility
Merge pull request #579 from BenMorel/cleanup

Unit tests: cleanup of outdated / unused / commented out code