truncate potentially long CompositeErrors

If you have a typo in a task on 100 engines, the local exception will be a bit ridiculous.

This defaults the truncation to 4 tracebacks (could be even fewer, or even one?),
and you can set the tb_limit attribute of CompositeError to adjust this.

Prompted by [this SO question](http://stackoverflow.com/questions/14635935/silence-or-condence-ipython-parallel-exceptions).
make baseProjectUrl a method in Menubar
add option in menubar to set baseproject url
make base project url a method on notebook list
change more baseurl
pass baseUrl as option
next release will be 1.0
Revert "patch deletion in codemirror"

This reverts commit 331a5f7fe85a6e894c35b64cd7987ed53f59ea57.
monkey patch codemirror with new functionality

use marijnh recommended way:
https://github.com/marijnh/CodeMirror/pull/661
update cm update instruction
Make CodeMirror configurable

Both on a per class and per instance basis, using an option dict
in constructor and per class dict
fix default empty option
Respect DB_IP and DB_PORT in mongodb tests.

It is usually preferred to run tests on a test-local database with
dedicated mongod instance rather than using the system-wide database.
In order to support that, an easy way of providing the proper port
is handy.

For example, pymongo test suite uses DB_IP and DB_PORT environment
variables to allow providing an alternate mongod instance. Using
the same variable names in IPython's test suite seems a good idea.
display order in output area configurable
Method to show hide linenumber of cell

mostly convenience methods to wrap codemirror one,
plus doc and 1 doc fix (missing curly bracket)
Use inputhook_wx2 on osx

Fixes #2762
Update docs/source/interactive/htmlnotebook.txt

Added a section on configuration. Still need to add a link to the general configuration page.
Update docs/source/interactive/htmlnotebook.txt

Added links to IPython configuration page.
Don't add logging handler if one already exists.

If a default handler already exists, it is expected that IPython is embedded in
an application that uses logging.  In that case IPython should not provide its
own logging handler, but rely on the embedding application's handlers.
Fix docstring of _log_default.