#1362 Add more error information to DTF InstallerExceptions

[Brian Rogers]

Deferred custom actions cannot access many of the properties in the MSI session (Database, Components, etc.). When a DTF custom action attemps to access them, exceptions are thrown, but they contain no information about the error that actually happened. We should detect this condition and provide a helpful error message.

[Jason Ginchereau]

DTF will throw a more informative exception when accessing any session properties not available from a non-immediate custom action.

[SourceForge Robot]

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