osgeo4w: more 'improvements'
 * package(64).cmd:
  * remove apps/%PACKAGENAME% before install (ie. don't repackage old cruft)
  * context_help, function_help, qgis_help.db, delimitedtextplugin.dll and diagramoverlay.dll removed in 2.0
 * package64.cmd: cmake is in PROGRAMFILES(X86)
 * nsis: adapt WelcomeFinishPage.bmp format for NSIS (ie. resave in paint)
 * nsis: installer don't use 64bit settings when installing 32bit package on 64bit OS