Make error_id used by filters configurable

Implemented for net.stubbles.ipo.request.filters.stubHTTPURLFilter in changeset 1029.

Implemented for net.stubbles.ipo.request.filters.stubMailFilter in changeset 1030.

implemented for net.stubbles.ipo.request.filters.stubFloatFilter and net.stubbles.ipo.request.filters.stubIntegerFilter with changeset 1031

Implemented for net.stubbles.ipo.request.filters.stubPasswordFilter with changeset 1032.

Outstanding: implementation for string filters (will be done by rist), adjustment of broker filter annotations to the new feature.

The implementation needs to be refactored, the current way has too much of the same code spread over several classes. Idea:

1. Introduce a new interface

interface stubConfigurableError extends stubFilter
{
    public function setErrorId($type, $errorId);
}

2. Introduce a new abstract filter class:

abstract class stubAbstractConfigurableErrorFilter extends stubAbstractFilter implements stubConfigurableError
{
    public function setErrorId($type, $errorId)
    {
        if (isset($this->errorIds[$type]) === false) {
            throw new stubIllegalArgumentException('Illegal type ' . $type . ' given. Allowed types are ' . join(', ', array_keys($this->errorIds)) . '.');
        }
        
        $this->errorIds[$type] = $errorId;
    }
}

Change all current implementations to inherit from the new abstract class.

The name stubConfigurableError needs to be reconsidered, I didn't come up with a better one until now.

Much better idea: throw away all implementation in the filter classes. Instead create a decorator for the error value factory that contains a mapping of error ids. The filter will not notice if it gets the real factory or the decorated factory and therefore not know which real error it is creating. Additionally this means the feature is only available for filters that use the factory, which was the original intention.

Added net::stubbles::ipo::request::stubRequestValueErrorFactoryMappingDecorator, reverted all previous implementations.

To change the error actually used by the filter do the following:

$rveFactory = new stubRequestValueErrorFactoryMappingDecorator(new stubRequestValueErrorXJConfFactory());
$rveFactory->addMapping('FIELD_EMPTY', 'MY_NEW_ERROR_ID');
$filter = new stubStringFilter(rveFactory, $regexValidator);

The filter will now try to create the error value with id FIELD_EMPTY, but the stubRequestValueErrorFactoryMappingDecorator takes care and maps this to MY_NEW_ERROR_ID.

Still to do: enhance documentation about request, filters and validators. Implement this for the broker filter annotations.

Note: the change above was done with changeset 1037.

Changeset 1042 implements configurable error ids for request broker: every filter annotation now supports the errorMapping argument, in format errorMapping='OLD_ERROR_ID1=>NEW_ERROR_ID1:OLD_ERROR_ID2=>NEW_ERROR_ID2'.

Documentation updated.