support for net45 and make baseurl writable for testcase usage

[Ali-YousefiTelori]

support for net45 and make baseurl writable for test case usage.

[hosseinRezaei188]

base url must be private to be prevent from edit in top layer

[Ali-YousefiTelori]

@hosseinRezaei188
We need to change it from the top layer.
you can see test cases of this project:
https://github.com/EasyMicroservices/SMS.git

the test cases are virtual, we don't need to send requests to the Kavenegar server to check our requests and responses are ok.
with this feature we can change the base URL of Kavenegar to localhost and send requests to virtualized server then we give a virtual response from the localhost.
So we can test our services without sending any request to Kavenegar to check the programmer requests are ok.