Feature/hpc checks

[cleibstein]

The additionally implemented check functions have been written to check the status of our HPC systems. But as it uses a generic JSON data structure as input, it can be used also in further use cases. In our use case, the first function "check_slurm" checks whether the SLURM batch system working on the HPC system is up.
The second function "check_nodes" gives back the number of nodes which are currently available , not working etc. On the status page itself, there will be a separate box which shows the number of according nodes. Therefore, the HTML script has some additional lines of code.

For the systems to be examined, one needs a JSON file which holds all of the relevant information. Such a JSON file could look as follows:

{"timestamp" : 12345678,
"systems" : {
"hpc_system1" : {
"state" : "up",
"nodes" : {
"Allocated" : 100,
"Idle" : 20,
"Other" : 0,
"Total" : 300
}
},
"hpc_system2" : {
"state" : "up",
"nodes" : {
"Allocated" : 200,
"Idle" : 30,
"Other" : 10,
"Total" : 3000
}
}
}
}

Everything else needed can be added in the checks.yaml configuration. While there are new components to be added, the structure is based on the previous entries.