Fixes for modern readline

Should address issues described in takluyver#117 et al. 

Additionally, I've added code to set the TERM_PROGRAM and TERM_PROGRAM_VERSION env vars so others can set variables accordingly. This *might* not be ideal, as perhaps bashrc has executed before these are set. Please advise if that's the case.

bash_kernel/kernel.py

@@ -107,6 +107,10 @@ def _start_bash(self):
 
         # Register Bash function to write image data to temporary file
         self.bashwrapper.run_command(image_setup_cmd)
+        # Set TERM_PROGRAM and TERM_PROGAM_VERSION. See https://github.com/takluyver/bash_kernel/issues/117#issuecomment-1032738154
+        self.bashwrapper.run_command(f"export TERM_PROGRAM='jupyter_bash_kernel'; export TERM_PROGRAM_VERSION='{__version__}';")
+        # Disable bracketed paste (see https://github.com/takluyver/bash_kernel/issues/117)
+        self.bashwrapper.run_command("(bind 'set enable-bracketed-paste off' || true) >/dev/null 2>&1")
 
     def process_output(self, output):
         if not self.silent: