Added some entity property accessibilities.
Added delta adjustment of entity positions.
Formatting; version update.
Menu callbacks need index param; 2.0.0-alpha.

The only reason that this commit leads to a 2.0.0-alpha release is
because it introduces backward-incompatible changes to the API (despite
it being alpha so it really doesn't matter anyway, but still), and thus
the major version must be incremented as per the "Semantic Versioning"
specification.

As a result, the alpha milestone is expected to have many major-version
updates, as is the nature of an alpha. Upon a 1.0.0-beta and a 1.0.0-rc
there will be much fewer major version updates that break the API.
Draft of a basic socket API.
Added comments and some debug logging.
Pong game (tries) testing networking API.
Track connection.
Added socket API initialization to core code.
Added socket API documentation.
Moved file to the right place.