…num" will automatically generate annotations that HDL backends can use to mark components as enums

Removed "override val width" constructor parameter from "Element" so that classes with variable widths, like the new strong enums, can inherit from it

Changed the parameter types of certain functions, such as "switch", "is", and "LitArg.bindLitArg" from "Bits" to "Element", so that they can take the new strong enums as arguments

…that the correct types of exceptions are thrown

…s used in multiple circuits

Made styling changes to StrongEnum.scala

Added an isValid function that checks whether or not enums have valid values

Calling getWidth on an enum's companion object now returns a BigInt instead of an Int

…unction is now simply a wrapper for StrongEnum.apply(n)

* Renamed "castFromNonLit" to "fromBits"

…th a class and a companion object for each strong enum

* Strong enums do not have to be static any longer

…into strong-enums

* Renamed ChiselEnum.E to ChiselEnum.Value to better match Scala enums

…ll it

outside of a ChiselEnum definition

* Renamed ChiselEnum.Value type to ChiselEnum.Type so that we can give
it a companion object just like UInt and Bool do

* Non-literal UInts can now be cast to enums with apply() rather than
fromBits()
* Reduced code-duplication by moving some functions from EnumType and
Bits to Element

…into strong-enums