Use minor upgrade mechanism for updates, set installer versionautomatically

src/engine/Updater.cpp

Index: src/engine/Updater.cpp
===================================================================
--- a/src/engine/Updater.cpp
+++ b/src/engine/Updater.cpp
@@ -115,17 +115,17 @@ void Updater::Update()
             dict->Lookup("updater", "download-error-title").c_str(),
             0);
       }
       if (result != IDOK)
         return;
     }
 
     {
-      UINT result = ::MsiInstallProductW(tempFile.c_str(), L"ACTION=INSTALL INSTALLUILEVEL=2");
+      UINT result = ::MsiInstallProductW(tempFile.c_str(), L"ACTION=INSTALL INSTALLUILEVEL=2 REINSTALL=ALL REINSTALLMODE=vomus MSIENFORCEUPGRADECOMPONENTRULES=1");

[Eric, 2013/06/11 15:41:46]

We can't always use minor upgrades for all upgrades, just some of them. I don't
know at this point if this syntax will support major upgrades or not.

See http://msdn.microsoft.com/en-us/library/aa370037%28v=vs.85%29.aspx . From
that page "A minor upgrade can be used to add new features and components but
cannot reorganize the feature-component tree." Moving the 32-bit DLL from the
64-bit Program Files to the 32-bit one is exactly such a modification. We'll
need to use a major upgrade to make that change. It might be the case that this
is the only one of those we'll ever need, but I doubt it.

This code has already shipped out. If this doesn't work for major upgrade, it
likely means that we'll need to make a (first) minor upgrade to change this so
that we then make a (second) major upgrade.

[Wladimir Palant, 2013/06/12 09:46:34]

Yes, most of them I hope.
Not trivially.
http://community.flexerasoftware.com/showthread.php?178239-msi-major-upgrade-...
indicates however that REINSTALL and REINSTALLMODE parameters can be reset in
the installer in case of a major upgrade. That's something to be tested before
our first major upgrade. If it comes really bad then we will have to ship a
minor update removing these parameters before we ship the major update.
There is a better explanation on
http://msdn.microsoft.com/en-us/library/windows/desktop/aa370093%28v=vs.85%29....
My impression is that moving a component to a different location is fine, merely
removing it is problematic. But that's something we will find out soon enough.

[Eric, 2013/06/12 14:33:24]

I'm going to open a Discourse thread on this topic. I think we can handle this
without the overhead you're worried about, but it relies on an msi.dll call I
need to look up.

       if (result != ERROR_SUCCESS)
       {
         Dictionary* dict = Dictionary::GetInstance();
         std::wstringstream message;
         message << dict->Lookup("updater", "download-error-runerror");
         message << std::endl << L"(error " << result << L")";
         MessageBoxW(NULL,
             message.str().c_str(),