notebookapp: add missing whitespace to warnings
add IPython.get_ipython

library entry point for get_ipython

does not rely on injection into globals
Don't rely on `get_ipython` in builtins in library code
don't use deprecated ipapi.get

It's been deprecated for three releases.  Come on guys.
remove reference to nonexistent 0.14 in deprecation warning
move core.ipapi -> core.getipython
remove deprecated `get`
Moving handlers to subdir
Adding new files.
Splitting handlers into different files.

I have also created a top-level utils.py for notebook related stuff
Adding __init__.py
Fixing url join problems.
Removing debug message.
define `__file__` in config files
More work on the handlers
Reorganizaing the server side of the notebook.
Updating import statements after moving notebook files around.
Renaming api handlers and moving FileFindHandler into base handlr.
Renaming templates to match other names.
Strip prompts even if the prompt isn't present on the first line.

Users (including me) often copy and paste examples from just after the first
prompt. This checks for prompts in the first two lines of a block, but if they
aren't found there, it will ignore prompt-like prefixes in later lines, to
minimise interference with multi-line strings etc.

Closes gh-3206