Add mochad component (#3970)

This commit adds a new component for communicating with mochad[1] a
socket interface for the CM15A and CM19A USB X10 controllers. This
commit leverages the pymochad library to interface with a mochad socket
either on a local or remote machine. Mochad is added as as a generic
platform because it supports multiple different classes of device,
however in this patch only the switch device implemented as a starting
point. Future patches will include other devices types. (although
that's dependent on someone gaining access to those)

[1] https://sourceforge.net/projects/mochad/

homeassistant/helpers/config_validation.py

@@ -2,6 +2,7 @@
 from collections import OrderedDict
 from datetime import timedelta
 import os
+import re
 from urllib.parse import urlparse
 from socket import _GLOBAL_DEFAULT_TIMEOUT
 
@@ -336,6 +337,14 @@ def url(value: Any) -> str:
     raise vol.Invalid('invalid url')
 
 
+def x10_address(value):
+    """Validate an x10 address."""
+    regex = re.compile(r'([A-Pa-p]{1})(?:[2-9]|1[0-6]?)$')
+    if not regex.match(value):
+        raise vol.Invalid('Invalid X10 Address')
+    return str(value).lower()
+
+
 def ordered_dict(value_validator, key_validator=match_all):
     """Validate an ordered dict validator that maintains ordering.