Fix file format documentation inconsistency against implementation

[jassielof]

Fixes related to #346:

• Makes both the entry and affiliated role types fully case insensitive.
• The file format now explains that the affiliated can be either a single object or a list.
• Removed outdated sentence case element from the basic test.

For the affiliated I initially wanted to not allow single objects, but well, it feels more convenient than having a single element list for it.

For the timestamps, the validation or enforcement regarding the format wasn't valid with the overflow, not sure if this was intended or well 😞.

Also, if might be relevant to fix some examples in #36, with clarification or just commenting on the issue?

[jassielof]

Actually, for the sake of simplicity, I feel that the entire thing of entry and role types shouldn't be much of fully case insensitive now 😔, mainly because of the JSON Schema, at least with the draft 7, it doesn't support case insensitive enumeration, nor case insensitivity in regular expressions. And more up to date drafts/specifications aren't widely or generally supported yet.

For the role types it's easier to make it into the schema with an enumeration, but with the entry types it gets different since one must retype both "article" and "Article" in the enumeration, or well if easier with regular expression just [Aa]rticle|... but then it gives a bit of bad feedback for the completions, in editors as it throws that it doesn't match the whole regular expression, compared to a nice list of accepted values. So, for the entry type at least would probably correspond removing the alias? But yeah, breaking changes 😞.

For the rest, I feel it's fine, maybe? 😭