Add enabledpatches config option

The server administrator must now specify which patches they want the
server to load (if deviating from the defaults). There are multiple
reasons for this:

* It's useful to be able to pick and choose which patches you want to
boot the server with; without having to move the directories in and out
of the patch directory
* This way, we can have different default patches for different builds
of the game (104 vs 1013)
* ...ergo, it's easier to rapidly switch builds without having to
rearrange your workspace to properly run them
* This also allows us to remove the std::filesystem stuff, which has
spotty compatibility with slightly older (but still current) versions of
the compilers

config.ini

@@ -40,6 +40,11 @@ motd=Welcome to OpenFusion!
 # location of the patch folder
 #patchdir=tdata/patch/
 
+# Space-separated list of patch folders in patchdir to load from.
+# If you uncomment this, note that Academy builds *must* contain 1013,
+# and pre-Academy builds must *not* contain it.
+#enabledpatches=1013
+
 # xdt json filename
 #xdtdata=xdt.json
 # NPC json filename