netdata: add new package

netdata: add new package

Netdata (https://github.com/firehol/netdata) is a real-time performance monitoring tool.
This submission uses the current Git prerelease, as the latest stable (1.1.0)doesn't build cleanly.

The default configuration makes a few changes for OpenWrt:
 - access log is disabled by default; too verbose for the circular
     syslog buffer, and logging to /tmp is risky memory-wise.
     Some sort of external device would be ideal for this.

 - error and debug logs are sent to OpenWrt's syslog

 - history and frequency times are halved to reduce memory usage,
     as recommended in the netdata wiki

 - external plugins are disabled to eliminate the dependency on bash
     and node.js. Those could be installed from OpenWrt packages if
     you wish to enable that functionality.

     All of those files are still present in the package. The installed
     size could be reduced by eliminating those files first.

Signed-off-by: Claudio Leite <[email protected]>
Signed-off-by: Sebastian Careba <[email protected]>
[squash commits, change PKG_VERSION]
Signed-off-by: Etienne CHAMPETIER <[email protected]>