Updates to simplify and clarify defining data for light sources

[lupestro]

The work here is intended to address the difficulties users have been encountering creating the JSON for light sources, as discussed at length in issues #23, #27, and #29.

• Code supports permissive JSON:
  • Eliminates the redundancy that used to be required between keys and the system and source values.
  • Provides sensible defaults so any of the fields that aren't interesting for the user's task at hand can be omitted.
  • Adds aliases so naming can be adjusted without having to copy the entire source details with a new name.
• More helpful README
  • Updated the documentation of each of the fields to make it clear what the user should do
  • Added documentation for how to characterize a system for purposes of detecting light sources and managing inventory
  • Added documentation for how to determine the actual names of animation and coloration types
• Added aliases to out-of-the-box light sources to address differences in naming of light sources between dnd5e compendia and ddb-importer.
• Adjusted names of settings from too-vague "GM/User Uses Inventory" to more-specifc "GM/User Consumes Inventory" to clarify what they actually govern.

[lupestro]

With a little more thought and a fifteen minute walk, I realized that the aliases need to be newValue: oldValue, not oldValue: newValue. I had originally thought of the latter as comparable to translation key: value files. However, suppose that the game needs multiple aliases for the same original value. Doing them separately with the current syntax, we'd end up with duplicate keys. We could make the value an array of new names, but it would be much simpler to turn it around, so that we define the target for each new name separately. It's also much more intuitive for the user, I think, to have the key be the term you're defining, and the value being what it refers to.