Support for username- und password-based authentication

[mback2k]

Since the device installation wizard already provides the functionality to specify username and password that are then stored within the device registry key, the following missing pieces need to be added:

• Retrieve username and password from device registry key
• Supply username and password for resources which require authentication

[mback2k]

Current progress can be tested with wiasane-v0.0.0.5-50-gb22d164. The following functionality is implemented:

• Retrieve username and password from device registry key
• Supply username and password for resources which require authentication (including CoInstaller)
• Support for MD5 password hashing during authorization (if supported by saned)

The following improvements are still pending:

• Make the CoInstaller pages actually check for device access and properties
• Make it possible to require/enforce MD5 password hashing
• Add a new callback type with support for user-defined context data