Move to YAML config and allow split functions

1. Move to a YAML-based configuration format instead of the original
   INI-based configuration to facilitate better organization and
   readability.
2. Modify the daemon to be able to operate in several modes based
   on configuration flags. Either networking or storage functions
   can be disabled using the configuration, allowing the PVC system
   to be used only for hypervisor management if required.

node-daemon/pvcd.sample.yaml

@@ -11,6 +11,15 @@
 pvc:
   # node: The (short) hostname of the node, set during provisioning
   node: pvc-hv1
+  # functions: The daemon functions to enable
+  functions:
+    # enable_hypervisor: Enable or disable hypervisor functionality
+    # This should never be False except in very advanced usecases
+    enable_hypervisor: True
+    # enable_networking: Enable or disable virtual networking and routing functionality
+    enable_networking: True
+    # enable_storage: Enable or disable Ceph storage management functionality
+    enable_storage: True
   # cluster: Cluster-level configuration
   cluster:
     # coordinators: The list of cluster coordinator hostnames
@@ -19,6 +28,7 @@ pvc:
       - pvc-hv2
       - pvc-hv3
     # networks: Cluster-level network configuration
+    # OPTIONAL if enable_networking: False
     networks:
       # upstream: Upstream routed network for in- and out-bound upstream networking
       upstream:
@@ -43,8 +53,9 @@ pvc:
         # network: Cluster storage network block
         network: "10.254.0.0/24"
         # floating_ip: Cluster storage floating IP address for the primary coordinator
-        floating_ip: "10.255.0.254/24"
+        floating_ip: "10.254.0.254/24"
   # coordinator: Coordinator-specific configuration
+  # OPTIONAL if enable_networking: False
   coordinator:
     # dns: DNS aggregator subsystem
     dns:
@@ -105,6 +116,7 @@ pvc:
         # stdout_logging: Enable or disable logging to stdout (i.e. journald)
         stdout_logging: True
       # networking: PVC networking configuration
+      # OPTIONAL if enable_networking: False
       networking:
         # devices: Interface devices configuration
         devices: