Added a data sheet viewer. It improves upon the design used in gta02-core by

allowing a hierarchy of caches, by using only one directory for each cache,
and by putting only one command in the PATH.

- scripts/dsv: new and improved data sheet viewer (successor of gta02-core's
  dsv)
- Makefile: added "dsv" target to update the bookshelf
- ds/INFO, components/INFO, modules/INFO: ds/INFO moved to BOOKSHELF
- components/INFO, modules/INFO: renamed "D" tag to "N", for consistency with
  BOOKSHELF
- BOOKSHELF: changed "stdpass" URL to the actual PDF

modules/INFO

@@ -2,12 +2,12 @@
 # Tags:
 #
 # F	Footprint name (must be first)
-# D	Data sheet identifier (N tag of ds/INFO; can be omitted if equal to F)
+# N	Data sheet identifier (N tag of BOOKSHELF; can be omitted if equal to F)
 #
 
 # TI meandered inverted F antenna
 F: meander
-D: AN043
+N: AN043
 
 # Mini-USB B receptable (SMT; almost generic)
 F: mini_usb_b