Adds option to ignore mounts via config file

This allows you to configure eZ Server Monitor to ignore certain disks
via the "ignore_mounts" option in the configuration file. You can either
create no "ignore_mounts" option at all, or set it to [] if you want to
show all mounts. To ignore certain mounts, add the exact mount path to
the array, e.g. ["/mnt/disk1"] or ["/mnt/disk1", "/mnt/disk2"].
This is done with *exact* string matching, so make sure the entries are
correct. This makes it possible to ignore "/" and still show other
paths.

conf/esm.config.json

@@ -12,7 +12,8 @@
     },
     "disk": {
         "show_tmpfs": false,
-        "show_filesystem": true
+        "show_filesystem": true,
+        "ignore_mounts": []
     },
     "ping": {
         "hosts": [