Fix several issues with our init script

- replace `"` with `'` as appropriate
- allow `DOCKER_DIR` to be configured via "/var/lib/boot2docker/profile"
- add `DOCKER_LOGFILE` variable to control where the daemon logs go, and switch them from overwrite to append
Output from "ping" is distracting and irrelevant

... especially on QEMU, where we can't ping out, so it just prints to the console endlessly
Merge pull request #471 from tianon/init-issues

Fix several issues with our init script
Merge pull request #472 from tianon/ping-output

Output from "ping" is distracting and irrelevant
change bootsync.sh to bootscript.sh and output console to /boot.log

change bootsync.sh to bootscript.sh
and create new bootsync.sh invoke the bootscript.sh ,logging info to
/boot.log ,so we can see what's wrong...
a few cleanups and use tee to log to screen and file.
start cleaning up some things
disable the kernel boot line automated pxe script - it uses bash
add extra log files for spawned processes, so tee doesn't block