Refactor HttpClient to handle user info provided in URI

[valfirst]

org.vividus.http.client.HttpClient#doHttpGet(java.net.URI) and org.vividus.http.client.HttpClient#doHttpHead(java.net.URI) should handle user info in the fully automated way:

• the methods should convert user info provided as a part of URI to basic auth configuration;
• these methods should be overloaded to accept parameter usePreemptiveBasicAuthIfAvailable;
• the default behavior should be non-preemptive basic auth;
• other methods accepting ClassicHttpRequest and/or HttpContext should be kept untouched;
• Javadocs for updated and created methods should be created.

Once it's done, one more refactoring should be performed: add a new field to org.vividus.http.client.HttpResponse - org.apache.hc.core5.http.protocol.HttpContext used for HTTP request execution.

The following parts of the codebase should be refactored after the implementation:

1. vividus/vividus-plugin-web-app/src/main/java/org/vividus/steps/ui/web/PageSteps.java

   Lines 332 to 344 in 2668dd0

   	URI pageUriToCheck = pageUrl;
   	UserInfo userInfo = UriUtils.getUserInfo(pageUriToCheck);
   	ContextBuilder contextBuilder = ContextBuilder.create();
   	if (userInfo != null)
   	{
   	UsernamePasswordCredentials credentials = new UsernamePasswordCredentials(userInfo.user(),
   	userInfo.password().toCharArray());
   	HttpHost host = HttpHost.create(pageUriToCheck);
   	contextBuilder = contextBuilder.preemptiveBasicAuth(host, credentials);
   	pageUriToCheck = UriUtils.removeUserInfo(pageUriToCheck);
   	}
   	HttpClientContext context = contextBuilder.build();
   	httpClient.doHttpHead(pageUriToCheck, context);

2. vividus/vividus-plugin-web-app-to-rest-api/src/main/java/org/vividus/crawler/SiteMapParser.java

   Lines 66 to 84 in 2668dd0

   	ContextBuilder contextBuilder = ContextBuilder.create();
   	UriUtils.UserInfo userInfo = UriUtils.getUserInfo(siteMapUrl);
   	URI targetSiteMapUrl;
   	if (userInfo != null)
   	{
   	targetSiteMapUrl = UriUtils.removeUserInfo(siteMapUrl);
   	BasicCredentialsProvider credentialsProvider = new BasicCredentialsProvider();
   	AuthScope authScope = new AuthScope(HttpHost.create(targetSiteMapUrl));
   	credentialsProvider.setCredentials(authScope,
   	new UsernamePasswordCredentials(userInfo.user(), userInfo.password().toCharArray()));
   	contextBuilder.useCredentialsProvider(credentialsProvider);
   	}
   	else
   	{
   	targetSiteMapUrl = siteMapUrl;
   	}
   	HttpClientContext context = contextBuilder.build();
   	HttpResponse response = httpClient.doHttpGet(targetSiteMapUrl, context);