Fix issue 806

Fix #806
Default connection is no more required

In `runtime` and `generator' sections, `defaultConnection` property is no more
required. The default is set up in the
`\Propel\Common\Config\ConfigurationManager::process()` method directly.
This commit fixes #793
Configuration refinements

Improve the code quality of the configuration sub-system:
remove some duplications, reduce method complexity, remove some unused code,
add some new test cases, improve code coverage, fix some code standard mistakes.
Merge pull request #808 from cristianoc72/config-refinement

Configuration refinements
Merge pull request #810 from cristianoc72/issue-793

Default connection is no more required
Merge pull request #809 from cristianoc72/issue-806

Fix issue 806
Added `overwrite` option to SqlBuildCommand.

This removes the requirement to manually remove the sql.map file to generate a new one.
Removed defaultValue for `platformClass` in tree definition. Detect platform and reverseParser classes now in GeneratorConfig.
Fixed #812 - Added `copy_data_to_child` parameter to ConcreteInheritance behavior.
Actually take $DB_PW from the command line

Per http://propelorm.org/documentation/cookbook/working-with-test-suite.html#use-custom-configurationcredentials
Don't require $DB_PW
Merge pull request #813 from mattleff/take-mysql-setup-pw

Actually take $DB_PW from the command line
Fixed typo in ConcreteInheritance behavior.
Made the sorting in getSchemas per default by name.
Fixed migration with TRIGGERs.

DDL with TRIGGERs aren't possible with prepare statements. Removed prepared statements in migration commands.
Fix issue #791
Fix ignore `generator.platformClass` property

`generator.platformClass` property, in the configuration file, is
always overwritten by the default value of `platform` option, in
`Propel\Generator\Command\AbstractCommand` class.
This commit fixes that behavior.
Fixed bug with hydrating objects that belong to another object through a many-to-one relation.

This bug only occurs during disabled instance pooling, since the TableMap::populateObject returns
always a new object and related objects (one-to-many from this point of view) are each attached to
this newly created object, which results basically in wrong getXYs returning always one object.
Removed comment at the closing brace of Extension Query Classes to conform psr-1/psr-2
Merge pull request #820 from mpscholten/fix-code-style-of-query

Removed comment at the closing brace of Extension Query Classes to conform psr-1/psr-2