Apply mask for markings to enable co-existence with multiwan, mwan3 etc.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

Changes committed to the cerowrt original repo after the initial import here:
 - Better license & copyright statements, as requested
 - Fixed a minor bug in stopping sqm
 - Logging improvements
 - Dead code removed
 - Typos corrected

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

sqm-scripts is a new QoS system from Cerowrt / Bufferbloat.
I have tested it in my own community build.

More info at:
http://www.bufferbloat.net/projects/cerowrt/wiki/Smart_Queue_Management
http://www.bufferbloat.net/projects/cerowrt/wiki/Setting_up_SQM_for_CeroWrt_310

Dave Täht submitted this first via openwrt-devel mailing list in March 2014,
but that was not picked up before the switch to Github:
http://patchwork.openwrt.org/patch/5078/

Original code used as the base:
8ce2936110

I have modified:
- set the default interface to be eth1, like the Openwrt default.
- modified config to hide some of the advanced options by default
- beautified Makefile a bit
- added Toke Høiland-Jørgensen <toke@toke.dk> as the maintainer, as discussed
  in https://github.com/dtaht/ceropackages-3.10/issues/8#issuecomment-59215905

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>