enforce crosschain contract address set check

[SmartLayer]

The following case should be examined by the schema.

 Currently, we do not provide cross chain attributes and cross
 chain event watch and cross chain transactions. We will come up
 with a design for that. We cautiously leave out legit use-cases
 like multiple-chains refer to the orcale in the same chain, lets
 TokenScript become too difficult to understand or faulty to debug
 with. Cross chain situations must be handled explicitly.

 i.e. if you declare a holding contract with only one network ID,
 all other countracts must have exactly one address on that network
 ID (addresses on other network ID are ignored until a holding
 contract exists in that network ID):

 This is legit:

 <contract name="holding">
 <address network="1">xxx</address>
 <address network="2">xyy</address>
 </contract>

 <contract name="bridge">
 <address network="1">yyy</address>
 <address network="2">yxx</address>
 </contract>

 This is not legit:

 <contract name="holding">
 <address network="1">xxx</address>
 <address network="2">xyy</address>
 </contract>

 <contract name="bridge">
 <address network="1">yyy</address>
 </contract>