[WLANware] Attended Sysupgrade update

[Paul Spooren]

Hi all,

please excuse I did not write earlier! 

What has been done last couple of weeks:
* Write Blogpost [1]
* Split project into 4 packages (see above)
* Redesign database to heavily reduce space consumption
* Validate downloaded ImageBuilders with SHA256 and signatures
* Build first usable Luci view (thanks jow-)
* Add uci options for custom update server url
* Started to split update server in server and worker
* First two packages been accepted in openwrt package repo [2,3]

What should be done next week:
* Parse produced manifest and store information to enable reproducible builds
* Continue split of server/worker
* Create pull request for luci-app-attendedsysupgrade in luci repo [4]
* Test usign for signing created images

Best, 
Paul

[1]: https://blog.freifunk.net/2017/07/25/one-server-sysupgrade-second-report/
[2]: https://github.com/openwrt/packages/pull/4625
[3]: https://github.com/openwrt/packages/pull/4627
[4]: https://github.com/openwrt/luci