remove download scripts, consolidate into script

most of them were just calling the gitclone script,
so remove them.

the grub script was treating gnulib as a dependency.
i've now added the ability to grab 1 dependency, in
the gitclone script (it should be expanded later to
support multiple dependencies)

the gitclone script has been renamed to "fetch".
the "fetch_trees" script does more or less the same
thing, but calls "fetch" and handles multiple revisions
if a project needs that

this is more efficient, and slightly reduces the code
size of lbmk!

Signed-off-by: Leah Rowe <leah@libreboot.org>

resources/scripts/build/module/bios_extract

@@ -25,7 +25,7 @@ set -u -e
 # --------------------------------------------------------------------
 
 if [ ! -d "bios_extract/" ]; then
-    ./download bios_extract
+    ./fetch bios_extract
 fi
 
 printf "Building bios_extract\n"