Implement InternalOrPublicFieldToProperty analyzer

[Vannevelj]

The only fields an application should have are private and protected. public and internal fields should be a property instead. The only exception here is when they are const or static readonly.

This stems from the idea of encapsulation: outside members should access private and protected fields through a method to allow for validation.

Provide a CodeFix which makes the field private and adds a public or internal property, depending on what the field was defined as.

[Vannevelj]

Part of this code fix includes renaming the field ( #25 ) so that will have to be done first.