SPARK-1623: Use File objects instead of String's in HTTPBroadcast

This seems strictly better, and I think it's justified only the grounds of
clean-up. It might also fix issues with path conversions, but I haven't
yet isolated any instance of that happening.

/cc @srowen @tdas

Author: Patrick Wendell <pwendell@gmail.com>

Closes #749 from pwendell/broadcast-cleanup and squashes the following commits:

d6d54f2 [Patrick Wendell] SPARK-1623: Use File objects instead of string's in HTTPBroadcast
SPARK-1802. (Addendium) Audit dependency graph when Spark is built with -Pyarn

Following on a few more items from SPARK-1802 --

The first commit touches up a few similar problems remaining with the YARN profile. I think this is worth cherry-picking.

The second commit is more of the same for hadoop-client, although the fix is a little more complex. It may or may not be worth bothering with.

Author: Sean Owen <sowen@cloudera.com>

Closes #746 from srowen/SPARK-1802.2 and squashes the following commits:

52aeb41 [Sean Owen] Add more commons-logging, servlet excludes to avoid conflicts in assembly when building for YARN
[SPARK-1736] Spark submit for Windows

Tested on Windows 7.

Author: Andrew Or <andrewor14@gmail.com>

Closes #745 from andrewor14/windows-submit and squashes the following commits:

c0b58fb [Andrew Or] Allow spaces in parameters
162e54d [Andrew Or] Merge branch 'master' of github.com:apache/spark into windows-submit
91597ce [Andrew Or] Make spark-shell.cmd use spark-submit.cmd
af6fd29 [Andrew Or] Add spark submit for Windows
Adding hadoop-2.2 profile to the build