Fixed class generator ignoring use aliases for extended class

[allcode]

This PR contains a fix for the class generator when using a use alias for the extended
class.

Bug explanation

Before this patch, the class generator would ignore all use aliases. This resulted
in an incorrect extends class. For example:

$classGenerator = new ClassGenerator();
$classGenerator->setName('ClassName');
$classGenerator->setNamespaceName('SomeNamespace');
$classGenerator->addUse('Foo\\Bar', 'BarAlias');
$classGenerator->setExtendedClass('BarAlias');
echo $classGenerator->generate();

would result in:

namespace SomeNamespace;

use Foo\Bar as BarAlias;

class ClassName extends \BarAlias {}

When using an FQCN for the extended class, it would ignore the use statement:

$classGenerator = new ClassGenerator();
$classGenerator->setName('ClassName');
$classGenerator->setNamespaceName('SomeNamespace');
$classGenerator->addUse('Foo\\Bar', 'BarAlias');
$classGenerator->setExtendedClass('Foo\\Bar');
echo $classGenerator->generate();

would result in:

namespace SomeNamespace;

use Foo\Bar as BarAlias;

class ClassName extends \Foo\Bar {}

Fix explanation

This PR fixes the ClassGenerator by checking whether the extended class matches
one of the use statements.
It supports the following varieties:

Using an alias as the extended class

$classGenerator->setName('ClassName');
$classGenerator->setNamespaceName('SomeNamespace');
$classGenerator->addUse('Foo\\Bar', 'BarAlias');
$classGenerator->setExtendedClass('BarAlias');

will result in:

namespace SomeNamespace;

use Foo\Bar as BarAlias;

class ClassName extends BarAlias {}

Using an alias of the extended class namespace

$classGenerator->setName('ClassName');
$classGenerator->setNamespaceName('SomeNamespace');
$classGenerator->addUse('Foo\\Bar', 'BarAlias');
$classGenerator->setExtendedClass('BarAlias\\FooBar');

will result in:

namespace SomeNamespace;

use Foo\Bar as BarAlias;

class ClassName extends BarAlias\FooBar {}

Using an FQCN as the extended class

The class generator will replace the extended class with its alias, if an exact use
statement match is defined.

$classGenerator->setName('ClassName');
$classGenerator->setNamespaceName('SomeNamespace');
$classGenerator->addUse('Foo\\Bar', 'BarAlias');
$classGenerator->setExtendedClass('Foo\\Bar');

will result in:

namespace SomeNamespace;

use Foo\Bar as BarAlias;

class ClassName extends BarAlias {}

The class generator will replace the namespace of the extended class with its alias,
if an exact use statement match is defined.

$classGenerator->setName('ClassName');
$classGenerator->setNamespaceName('SomeNamespace');
$classGenerator->addUse('Foo\\Bar', 'BarAlias');
$classGenerator->setExtendedClass('Foo\\Bar\\FooBar');

will result in:

namespace SomeNamespace;

use Foo\Bar as BarAlias;

class ClassName extends BarAlias\FooBar {}

[weierophinney]

Thanks, @allcode!