Don't need the trailing slash on the base_url

Removing it makes it easier to allow a cross-origin request between the
parent and child process.
extract method to return the URL to the debugger GUI
Add method to store the process's parent base url after a fork in the child

The child will use it to allow a cross-origin request from the parent process's
debugger.
The post-fork modal now works
Give a name to the untrapped exception function
Add POD for Devel::hdb::Client