OpenWrt programs (ubus, uhttpd) ported to Ubuntu

PPA for OpenWrt on Ubuntu.
Of course, OpenWrt programs can't be fully supported on Ubuntu but partially this works. For example uhttpd on Ubuntu works pretty well.

To expose /www dir via http run:

    uhttpd -f -h /www -p 8080

Goals:
0. Ensure that you can compile and build OpenWrt programs on Ubuntu directly from sources i.e. `cmake; make install` without BuildRoot. Some programs like rpcd needs for some files that aren't installed from cmake but installed by Makefile from rpcd package.
1. Create environment for user applications to be ported from OpenWrt to Ubuntu. E.g. to seamlessly run yurt-blog. Port ubus, rpcd, jshn, jsonpath and uhttpd. It's fine to publish them just in PPA.
2. Some tools like jshn and jsonpath are extremely useful by themselves. Currently jshn is the only one tool that allows to work with JSON from shell scripts. Publish them to Ubuntu and Debian repositories to make widely accessible.
3. Some tools like uclient-fetch (wget) and uhttpd are great fast and light alternatives and some users may prefer them. Uci and Ubus may be also interesting to create a new applications that not even related to OpenWrt.
4. Create development environment for OpenWrt developers. Currently to test your rpcd script you have to upload it to OpenWrt device or VM. It will make easier to develop and debug OpenWrt programs directly in Ubuntu.
5. Port Luci: this is almost not possible because netifd won't work but something may work and be useful.

https://github.com/stokito/openwrt-ubuntu