3029: Do not use previous App directory and warn user when installing in existing directory

[krzywon]

Description

This PR changes the INNO setup in order to always select a default directory (C:\Sasview-), not the previous one SasView was installed in and warns the user if the directory already exists.

Fixes #3029
Refs #3030

How Has This Been Tested?

I downloaded the Windows installer generated on push and tested both of the above items work.

Review Checklist:

Documentation (check at least one)

• There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)

Licencing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)

[butlerpd]

code changes look reasonable (not that I know much about INNO setup). This is unfortunately a place where the version number has to be updated separately from what is in the init file.

Importantly installing 5.0.6 then installing this PR the installer defaults to suggesting the sasview-6.0.0 folder not the previously installed folder. Install works. Installing again without removing 6.0.0 still defaults to the same folder but brings up a warning that the folder exists and asks if we want to proceed. Doing so works though that is because we are installing exactly the same files.

Unfortunately this does not address #3030. Installing on top of 5.0.6 for example does produce the warning (which it did before) but if the answer is "yes" the installation is completely broken and will not start (as before).

Ideally if the answer the user gives is "yes overwrite" we should remove the folder and recreate it. However the minimum should be to remove the option and just say we cannot install as the folder already exists.

Perhaps that should be another PR? I am approving this as fixing #3029 only as I'm guessing that was the intent?

[butlerpd]

Never mind .. I see where indeed #3030 is being addressed separately. So this should be able to be merged.