Get the initial amount of resource of a mineral patch or a geyser

[richoux]

It would be nice to have a data in sc2::Unit to know the initial amount of resource in a mineral patch or a geyser (for instance, 8, 900, or 1800 for a mineral patch), to get the same information proposed by the BWAPI::UnitInterface::getInitialResources() method in BWAPI for Brood War.

This would allow bots to make the difference between real resources and blocking mineral patch containing just a quantity of 8 minerals, for instance. It would also allow bots to compute the quantity of initial resources available to all potential base locations.

I am currently developing a terrain analysis tool working with both SC1 and SC2 maps (https://github.com/richoux/Taunt). This feature exists in BWAPI, and it would be nice it also exists in cpp-sc2, so my tool can offer the same features on both games, for instance for spotting blocking minerals.