fix typo in DictDB.size_limit

limit meant to be 1GB, but typo made it 1MB
add DictDB to autogenerated config / help

for cull fraction, etc.
increase registration timeout

to highest of 10 seconds or 5 heartbeat periods

Should reduce stalled registration notices (#2996)
on resume, print server info again

This commit makes it possible to differentiate between many different
long-running notebook servers, where the original ip address and port
information printed at the beginning has scrolled out of the screen.

We save the server location string that gets printed on startup, and
re-print it when the user attempts to interrupt the server with Ctrl-C

Thanks to @minrk for discussion on how this should work.

Also added a docstring to the start() method
log the notebook server directory

suggestion provided by @Carreau
make SIGUSR1 and SIGINFO trigger printing of info

Directory and url/port information for the notebook server is now
printed when it receives one of these signals. SIGINFO is available only
on BSD-based systems, and is triggered via Ctrl-T.
cast kernel cwd to bytes on Python 2 on Windows

Popen on Windows Python 2.x apparently cannot handle unicode cwd.
use filesystemencoding if defined, fallback on ascii.

closes #3039
add width:100% to vbox for webkit / FF consistency

closes #3049
recompile less css
Merge pull request #3046 from minrk/popen_cwdu_win32

cast kernel cwd to bytes on Python 2 on Windows

Popen on Windows Python 2.x apparently cannot handle unicode cwd. use
filesystemencoding if defined, fallback on ascii.

closes #3039
test double pyximport
Merge pull request #3062 from juliantaylor/double-pyximport-test

test double pyximport (#3007)
print info string on interrupt, log it on startup
Merge pull request #3033 from ivanov/print-server-info

on resume, print server info again
Merge pull request #2997 from minrk/db_limit

fix DictDB default size limit

typo had the default size as 1MB, not the intended 1GB.
Also fix its exclusion from generated config.
Merge pull request #2999 from minrk/regtimeout

increase registration timeout

to highest of 10 seconds or 5 heartbeat periods.

Should reduce stalled registration notices.

closes #2996
Merge pull request #3051 from minrk/vbox-ff-fail

add width:100% to vbox for webkit / FF consistency

closes #3049
check for SIGUSR1 before using it, closes #3074

thanks @takluyver for spotting this
Merge pull request #3075 from ivanov/sigusr1-windows

check for SIGUSR1 before using it, closes #3074