Extract plugin helpers into a lib script

In both e:cue and QLC+ 4.11.2 (or 4.12.1 after #978 is merged) import plugins, there are some helper functions that try to guess capability type and type-dependent properties from the capability name. We should make them as general as possible and extract them to a lib script to reduce code duplication and improve maintainability.

Keep in mind that changes of this lib script should then also trigger GitHub tests (see also #988).

In particular, the getSpeedGuessedComment function needs to be extracted and cleaned up. Copied from https://github.com/OpenLightingProject/open-fixture-library/pull/978#discussion_r310933525 and https://github.com/OpenLightingProject/open-fixture-library/pull/978#discussion_r311223634:

This function sets some properties, but to ensure a consistent property order, a lot of extra logic is needed from where it is called. Furthermore, there are some (unexpected) side effect it does, for example setting the capability type.

It may be worth refactoring this to return an object { type, speedStart, speedEnd, comment } where any of the properties may be an empty string. Then set the cap data like so:

const { type, speedStart, speedEnd, comment } = guessSpeedData(capabilityName, cap);
cap.type = type || cap.type;
cap.effectName = comment;
if (speedStart) {
  cap.shakeSpeedStart = speedStart;
  cap.shakeSpeedEnd = speedEnd;
}

[Regarding the regular expression:] Is there a way to beat this beast of RegExp? Maybe use some RegExp.exec instead of a single replace.

Start with the e:cue and QLC+ 4.11.2 import plugins and locate getSpeedGuessedComment plus the other capability-guessing helpers. Review the linked #978 discussions and #988 for the expected refactoring and GitHub test behavior. Done means the helpers are shared through a lib script, the returned capability data is applied consistently, and changes to that script trigger the tests.