Rename "isSupportedContract" to "supportsInterface"

[chrisaxiom]

"isSupportedContract" is just made up, the correct method name is "supportsInterface"

cc @pazams

[pazams]

isSupportedContract(contract c) is a made up wrapper and defined to be equal to : c.supportsInterface(interface a) or c.supportsInterface(interface b)

Since a and b are hardcoded, it made sense to me to make the wrapper name different.

[chrisaxiom]

How about supportsInterfaces instead? Makes it clearer as to what it is actually doing.