Add dryRun mode

[szpak]

When dryRun property in task configuration is set the plugin should only display what would happen (what request with what parameters would be sent).

It is useful implementing dryRun mode in the build script in general (when one of the used plugins/tasks is rest-gradle-plugin).

[szpak]

Btw, in that mode password (when set) should not be displayed or should be masked.