Support for declaring all roku types in typedefs

We should have a way to declare all (or almost all) built-in roku types in typedefs. This would provide several benefits:

• more flexibility for contributors wanting to improve the documentation on the native types
• more options for separating certain features into different libraries (like brightscript, brightsign, maybe future versions of brightscript with new features)
• enables developers to use that same syntax to declare objects in their own code that might not be public knowledge (i.e. internal roku projects, select partners, etc).

I envision we move all of the built-in types and objects and components and interfaces into a single folder (maybe libs/brightscript.d.bs, and here is the syntax I'm currently envisioning.

• the native interfaces can probably just use the existing interface keyword

  interface ifDateTime
      sub ToLocalTime() as Void
     ...etc
  end interface
  

• "brightscript components" use the object keyword". We need a way to "spread" all of the functions of an interface onto the object. Maybe that's how "implements" works for object, or maybe we have some extra syntax to say "I'm not going to write them again, just copy them onto this thing".

  object roDateTime implements ifDateTime, ifToStr
      'objects can also have concrete methods declare on them, if you want to make an interface for them
      function someNonInteraceFunc() as integer
  end object
  

• components would use the component keyword (like the component statement syntax mentioned in #575)

  component "Rectangle" extends "Group"
      'callfuncs
      public getBoundingRect() as roAssociativeArray
      'fields
      public someField as roAssociativeArray
  end component
  

• Declaring these items with the declare keyword in a d.bs file might allow them to be exposed globally to the program. Like this:

  declare function abs(num) as number
  

Start by reviewing the proposed declarations in a possible libs/brightscript.d.bs file and the component statement syntax referenced in #575. Determine how interfaces, objects, components, and declare would fit together, then define a testable scope for built-in type declarations and global exposure; the issue does not identify existing implementation files or tests.