Allow filename with extension in find_cmd in Windows.

closes gh-3316 (hopefully)
Add a mode to exec code in %debug magic
Document the new usage of %debug
Drop patch for compatibility with pyreadline 1.5

Closes gh-1307
Set calling program to the empty string, when argv not in sys

It might happen, then the sys module has no argv, when embeding IPython
into other programs with IPython.embed(). In that case, just set the
calling program to "" or other logic in IPython will crash - for
instance when checking for command line arguments.
Added shorcuts to split cell, merge cell above and merge cell below.
Added '-' as a shortcut for splitting cells.
expand ANSI color support

adds support for 256 colors

does not yet add support for themed 16-color mapping ([01;38;5;[0-15])

closes #3617
add ansi background colors
add indexed-color in 256-color support
be pedantic about VT100 vs ANSI in comments
add ANSI color test notebook to examples/tests
raise UsageError for unsupported GUI backends

gives clearer, more concise message without traceback

closes #3609
Merge pull request #3071 from tkf/drun

Extend the `%debug` magic to also run a statement under the control of a debugger, if called with arguments.

If called with no arguments after an error has occurred, it continues to work as before.
Merge pull request #3623 from minrk/pylabusageerror

raise UsageError for unsupported GUI backends
Merge pull request #3618 from minrk/ansilinux

expand terminal color support (16 and 256 ANSI colors)
fix some unicode in zmqhandlers

prevented session identity from being set properly,
which in turn prevented stdin from working in the notebook in Python 3.

closes #3494
passing cell to showInPager, closes #3625
use DEFAULT_STATIC_FILES_PATH in a test instead of package dir

allows post installation tests with split static data to succeed
Fix test for Python 3 on Windows.

IPython.core.tests.test_run.test_aggressive_namespace_cleanup