Added Azure cost and pricing functions

[yueguoguo]

• Minor updates on config initialization.
• Added cost and pricing functions and their unit tests.

[msftclas]

@yueguoguo, Thanks for your contribution as a Microsoft full-time employee or intern. You do not need to sign a CLA. Thanks, Microsoft Pull Request Bot

[andrie]

Thank you. This is a great contribution.

Please can you modify your code as follows:

• Do not use dplyr or magrittr. This introduces a very large set of dependencies, for work that can easily be done using base R.
• Please use lowerCamelCase for object names. In a few places you use UPPERCASE names.
• Please wrap long lines manually at around 80 characters.

For roxygen documentation:

• Do not use the @title tag. Simply write the title of the function. This should be a single sentence. Any other words should go on a new line.
• Use @inheritParams where possible

[Alanwe]

Great addition, I had played with the billing APIs and I did think of some functions in this area. I can imagine some pretty cool plots could be added. The one challenge I became aware of is that it currently only supports PAYG(Not EA) so the rate card should be used with caution.

[yueguoguo]

@Alanwe Very good point. Thinking of putting notes somewhere. I am using Microsoft internal subscription, and currently have no way to test other offer options. Need advice. Cheers.

[andrie]

Thank you!