Refactor i2p.vmCommSystem configuration parameter.

In some cases, the i2p.vmCommSystem configuration parameter has been used as a surrogate for signifying a testing network.

However, VMCommSystem is a special, narrowly focused comm system implementation that is seldom used.

The i2np.allowLocal configuration parameter has been introduced to indicate testing/local networks, and should replace the instances where i2p.vmCommSystem was used solely to indicate a local/testing network.

Update the documentation to clarify the purpose of VMCommSystem, and migrate i2p.vmCommSystem to i2np.allowLocal where it was used to indicate a testing/local network.

Signed-off-by: obscuratus obscuratus@mail.i2p