Integrate expressions/functions with DSC

[SteveL-MSFT]

PR Summary

• Removed resourceId() regex and replaced with a function
• Add execution of expressions to get/set/test resource properties
• This integration allows use of concat() and base64() functions within a configuration
• Change from HashMap to serde Map for resource properties so don't need to transform from one type to the other due to nested properties
• Expressions are evaluated only for resource properties at invocation time
• NOTE: when converting Value to string, you have to use as_str() instead of to_string() as the latter includes outer quotes

PR Context

Partially implements https://github.com/PowerShell/DSC/issues/57

[SteveL-MSFT]

The test failure is due to not handling nested types in expression invocation so fixing that.

[SteveL-MSFT]

The remaining failure is due to properties that get returned may look like an expression so if you pipe that back to dsc, it fails. I think the right thing to do here is if it's retrieved via config, then it needs to escape it if it starts and ends with brackets.