If the timeout argument is a promise, abort the request when it is resolved.
Implemented by adding support to $httpBackend service and $httpBackend mock
service.

This api can also be used to explicitly abort requests while keeping the
communication between the deffered and promise unidirectional.

Closes #1159

Because ngDoc generation only takes the last segment of a property name,
each $log.[error|warn|log...].logs property has the same name and is
confusing in the docs.
This commit helps this by adding a link to the $log.* method and also an
appropriate usage example.

myApp.factory('myAroundInterceptor', function($rootScope, $timeout) {
    return function(configPromise, responsePromise) {
        return {
            request: configPromise.then(function(config) {
                return config
            });
            response: responsePromise.then(function(response) {
                return 'ha!';
            }
        });
}

myApp.config(function($httpProvider){
    $httpProvider.aroundInterceptors.push('myAroundInterceptor');
});

Change "constroctor" to "constructor".