service list, service info: output json

## before

```console
$ slapos service list
List of services:
erp5 /srv/slapgrid/slappart15/srv/project/slapos/software/erp5/software.cfg
slapos-sr-testing /srv/slapgrid/slappart15/srv/project/slapos/software/slapos-sr-testing/software.cfg
slapos-testing /srv/slapgrid/slappart15/srv/project/slapos/software/slapos-testing/software.cfg
hugo /srv/slapgrid/slappart15/srv/project/slapos/software/hugo/software.cfg
metabase /srv/slapgrid/slappart15/srv/project/slapos/software/metabase/software.cfg
dufs /srv/slapgrid/slappart15/srv/project/slapos/software/webdav/software.cfg
```

```console
$ slapos service info slapos-sr-testing
Software Release URL: /srv/slapgrid/slappart15/srv/project/slapos/software/slapos-sr-testing/software.cfg
Instance state: busy
Instance parameters:
{}
Connection parameters:
("<?xml version='1.0' encoding='utf-8'?>\n"
'<instance>\n'
'  <parameter '
'id="environment-script">/srv/slapgrid/slappart15/srv/runner/instance/slappart7/etc/slapos-local-development-environment.sh</parameter>\n'
```

## after

```console
$ slapos service list
{
  "dufs": "/srv/slapgrid/slappart15/srv/project/slapos/software/webdav/software.cfg",
  "erp5": "/srv/slapgrid/slappart15/srv/project/slapos/software/erp5/software.cfg",
  "hugo": "/srv/slapgrid/slappart15/srv/project/slapos/software/hugo/software.cfg",
  "metabase": "/srv/slapgrid/slappart15/srv/project/slapos/software/metabase/software.cfg",
  "slapos-sr-testing": "/srv/slapgrid/slappart15/srv/project/slapos/software/slapos-sr-testing/software.cfg",
  "slapos-testing": "/srv/slapgrid/slappart15/srv/project/slapos/software/slapos-testing/software.cfg"
}
```
```console
$ slapos service info slapos-sr-testing
{
  "software-url": "/srv/slapgrid/slappart15/srv/project/slapos/software/slapos-sr-testing/software.cfg",
  "instance-state": "busy",
  "instance-parameters": {},
  "connection-parameters": {
    "environment-script": "/srv/slapgrid/slappart15/srv/runner/instance/slappart7/etc/slapos-local-development-environment.sh"
  }
}
```


See merge request !441