Preserve configuration of a previous NSIS installation

[marbx]

We must use the configuration and preserve the cache of a previous NSIS installation,
stored in salt/var and salt/conf.

We achieve this by deleting everything else:

• stop and remove the salt-minion service
• Remove the registry entries
• delete C:\salt\uninstall.exe
• delete C:\salt\nssm.exe
• delete C:\salt\salt* (all the batch files)
• delete the C:\salt\bin directory

My current understanding is that RemoveFolder only removes an empty folder, and RemoveFolderEx is difficult to handle, I also anticipate many WiX resrtrictions.
I therefore prefer to extend the CustomActions in MinionConfigurationExtension

[marbx]

After several attempts with InstallExecuteSequence , I read
http://stackoverflow.com/questions/11668875/execute-a-custom-action-before-product-condition

[marbx]

Solved with the peelNSIS function.