Polish GDI01 and 02.

This fixes the landing craft in both missions, and includes additional tweaks to GDI01:
* Removes unbuildable concrete wall from production palette.
* Fixes chat sounds and reinforcement notification overlapping FMV.
* Cuts down the excessive starting forces to encourage base building.
This was from an earlier implementation attempt, but I thought it could be handy to have so I left it.  I can remove it if we want to minimize the changes introduced in this pr.