Add default AP[Otrego-Clamshell:0.1.0] property to new Movetrees

[artasparks]

When creating new games, we should add AP[Otrego-Clamshell:0.1.0] to new Movetrees. AP[Application:Version] means "this SGF was created by Application @ Version". We don't currently have a released version of Clamshell; 0.1.0 seems like a reasonable version number to start with.

Requirements:

• Should look like the GM property:
• Should have a basic unit test in movetree_test

Defaulting example for GM property:

g.Root.SGFProperties["GM"] = []string{"1"} // GM[1]=go