Systems now place all of their component factories into a `Components`
member. This improves code readability and makes it clear when we are
dealing specifically with ecs components.
The concrete ComponentFactory instances now have `Add` and `Get`
methods (as opposed to `AddAlpha` or `GetAlpha`). This enforces naming
of component factories as to avoid collisions when embedded in a struct
with other components.
Also, the ComponentFactory interface is embedded directly into the
concrete component factory without a name.
* common component methods have been put into BaseComponent and
BaseComponentMap
* boilerplate code for components has been significantly reduced
* all lint errors fixed in d2components
- adding components to handle font tables
- handle loading font tables in asset loader
- handle file type for font tables
- file handle resolver system now caches file handles
- asset loader system now caches loaded assets
