MSI: support for upgrades

[bpintea]

Currently, side-by-side installation of different driver versions is only supported if they are for different architectures (i.e. x86 and x64 drivers can co-exist).
This ticket tracks the feature to allow the installer do upgrades within the same architecture; for example a 7.0.1 x86 be upgraded to a 7.0.2 x86. (This currently requires uninstalling the 7.0.1 beforehand.)

[UlyssesWu]

What if I want to connect to 2 different ES, one is v6.8 and another is v7.4 ? The JDBC drivers can do that but ODBC can not.

[bpintea]

That's an ODBC limitation and requires that either the version is part of the driver name or the driver/server maintains backwards compatibility; the later is the common choice for most vendors and ES adopted it with 7.7 release (see this post); prior versions are version-step-locked.