Added support of WSDL import

[komalsukhani]

User can now import WSDL file to create API definition.
#Reference

Supported features:

1. WSDL file with multiple services
2. SOAP/SOAP12 binding
3. HTTP binding

Generated API Definition will be as follows:

1. API name is same as that of the service name. If WSDL contains multiple services, then the name of the first service in the file will be used.

2. listen-path of the API will be

"/service name/"

If WSDL contains multiple services, then the name of the first service in the file will be used.

3. For each supported operation, an endpoint will be created. Endpoint will have the path

/service_name/end_path

In case of SOAP/SOAP12 binding, end_path will be operation name.
In case of HTTP binding, end_path will be value of location attribute of the operation.

4. Each endpoint will use url-rewrite middleware to direct the request to the upstream. This was necessary to support multiple services

If service has multiple Ports type, name of the Port needs to be specified. If Port name is not provided then first Port of the service is used.

#2255

[matiasinsaurralde]

Looks good!

[buger]

It definitely misses some tests, when it reads example WSDL file, and compare converted version with expected.

[buger]

@komalsukhani pls create UI related ticket

[komalsukhani]

@buger Already created. Here is the link https://github.com/TykTechnologies/tyk-analytics-ui/issues/1182