Patch Windows installer env var script to not trash PATH

From http://nsis.sourceforge.net/Environmental_Variables:_append,_prepend,_and_remove_entries#Warning
Merge pull request #2 from eco/master

Patch Windows installer env var script to not trash PATH
Add "dman" command to deb/rpm packages, and correct some errors.
Merge branch 'master' of https://github.com/D-Programming-Language/installer
update dmd2 minimum version
Update to dmd 2.056
Automated installer creation for OSX
Using mktemp. Also made upload atomic to avoid truncated files on the server.
cosmetic
Now builds both D1 and D2 versions, can run with -j
Add script to build packages for Arch Linux
Add "xdg-utils" as dependency on dmd2 packages
Change lib installation dir on debian packages
add "ddemangle" executable on dmd2 packages
update dmd URL
Make D1 unchecked by default

New users sometimes have difficulty because they've installed both versions of
D which places both in their path, which means they sometimes try to compile
D2 code with D1.
Replace default NSIS welcome/finish graphic

Uses website graphics
Create shortcut to D1 and D2 documentation

But only create either shortcut if the user actually installed the
corresponding version.
Add custom icon to Windows installer
Merge pull request #6 from eco/help-start-menu-fix

Create start menu shortcut to D1 and D2 documentation
Merge pull request #5 from eco/installer-graphic

Replace default NSIS welcome/finish graphic with custom D graphics
Merge pull request #4 from eco/non-default-d1

Make D1 unchecked by default