Renamed http header parsing/creating files
Switch to using correct include paths instead of fixing it in Makefiles

This means the include paths can be resolved by the editor when editing, which makes it easier to edit
Moved http handler into plugin

Doesn't work yet because it needs access to functions defined in core
Moved include files (again)
Restructured (again)

Now the core source is treated as a library like the plugins

Now libraries can interdepend on each other (necessary for plugins to use functions from core)

Libraries are built in the order of their directory names, so if one needs to be built before another that can be handled by naming the directories accordingly (the library name can be redefined in the Makefile if neccesary - see core)