Add additional information for transportation units

[slannon97]

When viewing transportation units such as flying machines, there should be a way to check whether the unit has any units loaded into it and how many of a given unit is loaded. For example, it could tell you that flying machine 1 has 3 of 8 units loaded. This would help keep track of where all your units were. Currently, units that are loaded into transportation units simply disappear and there is no way to view them aside from unloading the transporting units.