Closes #1974

Situation:
==========

$ ls -l /lib/gluon/domains/lindennord.json
lrwxrwxrwx    1 root     root            10 Jan  6 03:42 /lib/gluon/domains/lindennord.json -> dom17.json

Before:
=======

$ gluon-neighbour-info -d ::1 -p 1001 -r nodeinfo -c 1
{
   "node_id": "525400123456",
   "system": {
     "domain_code": "lindennord",
     "site_code": "ffh"
   },
...
}

After:
======

$ gluon-neighbour-info -d ::1 -p 1001 -r nodeinfo -c 1
{
   "node_id": "525400123456",
   "system": {
     "primary_domain_code": "dom17",
     "domain_code": "lindennord",
     "site_code": "ffh"
   },
...
}

Provide the number of OWE stations in addition to the number of all
connected wireless clients.

In addition this PR contains:
- split of gluon-respondd provider into multiple source files
- minor additional cleanups in gluon-mesh-babel respondd provider
  (untested, as the babel respondd provider already doesn't compile prior
  to these changes...)

This commit adds information about:
- how cpu time is spent since boot in jiffies (1/100*sek) (cpu)
    - the value is summed for all cores, so in 10 seconds the
      summed values will increase by 4000, if the cpu has
      4 cores
- context switches since boot (ctxt)
- interrupt counters since boot (intr, softirq)
- forks since boot (processes)

    { "stat": {
       "cpu": {
         "user": 219403,
         "nice": 1714,
         "system": 75159,
         "idle": 2727739,
         "iowait": 2943,
         "irq": 0,
         "softirq": 571
       },
       "intr": 8426340,
       "ctxt": 50992590,
       "processes": 10549,
       "softirq": 5161884
    } }

[Matthias Schiffer: rebase]

Fixes #414

Most doubles that are delivered via respondd have limited input
precision, but are converted with up to 17 digits of precision. That can
cause ugly blowups like 0.2800000000000001 in the output, which is
avoided by specifying better format strings (like "%.2f" in most cases).

gluon-announced and gluon-announce are merged to gluon-respondd.