Added support for setting environment variables in the form of: set V1<installer param name>=value to override instsallation defaults.

Example:

```
set V1DBName=V1Db
set V1InstanceName=V1Agile
set V1DBServer=v1dbserver
cinst VersionOne -source '%CD%'
```

That will change from the defaults of:
VersionOne
VersionOne
(local)