env.properties is not used in *.bat files

Some of the *.bat files currently rely on AIR_HOME and PLAYERGLOBAL_HOME as environment variables. However, when using env.properties instead of setting the environment variables, they are not taken into account. Hence the *.bat files fail. This also causes errors for all processes that invoke the *.bat files (like the Mustella build).

I've changed the *.bat files to take env.properties into account, using an extra file that sets up the environment vars and that is now called in each *.bat file.