This is analogous to the DOM's Node.tagName and makes it easy to ask "hey, what kinda thing is this Node?"
This was a workaround to be able to build on case-insensitive file systems where it might get confused about <string.h> vs <String.h>. Let's just not support building that way, so String.h can have an objectively nicer name. :^)
Things were getting a little crowded in the project root, so this patch moves the Lib*/ directories into Libraries/.
