fixed problems with joined inheritance and composite keys

SchemaTool now creates all Id columns not just only the first one.
Insert statement for child entity now contains parameter for additional key columns only once.
inheritance with composite keys

added tests for single table inheritance
Unit tests: cleaned up outdated / unused / commented out code.
Remove dead code
Fix SimpleObjectHydrator behavior when column not exists in fieldMappings, relationMappings and metaMappings
Fixed broken code block in documentation
Reverted incorrect typo fix -_-
adds a new output format
Added $isIdentifierColumn documentation

I've added the documentation of the argument $isIdentifierColumn since in case of foreign composite keys it doesn't 
Adding EntityManagerDecorator base class as an extension point for EntityManager
Added 'contains' comparison
Added composer.lock to .gitignore
Fixed typos
Merge pull request #607 from pborreli/typos

Fixed typos
Fixed typo
Merge pull request #608 from pborreli/patch-1

Fixed typo
Fixed typo.
Merge pull request #609 from haroldb/patch-1

Fixed typo.
[BUGFIX] Correct link to Functions, Operators, Aggregates

This fixes the in-page link to the Functions, Operators, Aggregates
section.
Fixed typo in hints. Caused slow loading of eager entities.