Checking that the platform supports foreign key is not the right case
here, because we should check if we can create them by themselves, after
the table is created. It is not the case for Sqlite.

Closes #3990

The current implementation uses the schema name as namespace name.
Some platforms don't support schema's, but a namespace name still needs to
be present. Added namespace name 'default' when there is no default schema
name.

default schema name is public for postgresql not default. Added debug
statements to test travis-CI.

Put the responsibility to give the default schema name from CreateSchemaSqlCollector to the Platforms (abstract, sqlserver, postgresql)

The namespace is used as name for the database schema. For SQL Server the default schema name is "dbo" and not "default".

- Fixed docblocks
- Removed return statements on void methods
- Cleaned up unused private / local variables
- Fixed license issues
- Removed SVN leftovers
- Fixed doctrine-project.org links
- Added line breaks before return statements