Construction Tweaks

Makes slight changes to the game's Construction progression. Splits vanilla Basic construction into 2 phases. Idea behind this is that basic construction is really basic and survivors with the appropriate skill would know it from the start. Everything after would require some more effort and experience. Initially makes getting a real roof over their heads easier, pretty much normal progression after that. Basic Construction - - only allows building with Scrap, Sticks, and Wood (Logs) - requires a survivor with Construction skill 1 or greater - very quick to research (we'll call it your survivors planning phase) Intermediate Construction - - includes the rest of the basic materials Wood (Planks), Stone, and Metal (more difficult materials to work with) - requires a survivor with Construction skill 3 or greater Concrete, Brick, Carbon Construction - - increases the required skill level by 2