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.
Merge remote-tracking branch 'upstream/master'
Fixed constant names