[SFOS] Add automatic generation of configuration

[rinigus]

Taking into account that most of the users on Sailfish would use default directories and makeconfig script to generate configuration, it should be possible to generate the configuration automatically. Proposed scheme:

• user-specified dirs (use the current one) are checked for collectd datasets (like load/load.rrd). If this test is passed, proceed
• makeconfig is run against the specified dir and its stdout received by c++ object.
• makeconfig output is checked on whether its valid JSON (see if all required objects are defined)
• if all tests are passed, give the loaded file in string form to QML. In QML, proceed with loading configuration, as usual.

[rinigus]

fixed