Windows Makefile/NSI installer updates (Internet downloading!) plus bugfixes

Windows Makefile/NSI installer updates (Internet downloading!) plus bugfixes

Details:
* Makefile.win updated for current build environment, with lots of
  notes added about how to successfully build on Windows...  Still
  -not- a fun or easy process, though.
* installer.nsi updated to support internet downloading of optional
  dictionaries and stroke order diagrams and unzipping of optional
  packages.  EDICT2 and KANJIDIC are included in the installer
  without downloading, while KANJIDIC2 and both stroke order diagram
  packages are downloaded if the user desires them.  Source packages
  can also be installed through the Windows installer.
* SOD checkboxes are not auto-greyed in dialog_config.  This is
  because the flags they represented were not being cleared when
  SOD files were not found.  This is essentially a workaround until
  I solve the problem more gracefully.
* Bugfix in dialog_kanjitest: preference keys
  kanjitest.kanji{read,write} changed to kanjitest.{reading,writing}.
* kdict.cpp: Since GTKTextViews don't support animated SODs, only
  static SODs are used.  Animated SODs may still be used in the kanji
  test mode since the images are displayed using a different GTK
  control which allows animation.
* Small string changes in dialog_config, mainly to reflect the change
  in kdict.cpp
* Small change to widget_kanjihwpad, made while tracking down a
  Windows-specific error.  The changes are not vital, but I'm leaving
  them in.