Add reload4j support

[tbroyer]

See https://reload4j.qos.ch/

At a minimum:

• reload4j dependency should have the log4j:log4j capability to conflict with log4j:log4j, and should probably be added to slf4j-vs-log4j2-log4j
• slf4j-reload4j should be added as an slf4j implementation (added to slf4j-impl capability)

[tbroyer]

Working on a PR for this, it's not as easy as it seems, in the sense that ideally having log4j and reload4j in the graph should resolve the conflict using reload4j (highest version should be enough, on a new log4j-reload4j capability), but because both dependencies need to be added to the slf4j-vs-log4j2-for-log4j capability they'll conflict through that anyway.

Should a new default resolution strategy be created such that the slf4j-vs-log4j2-for-log4j capability could detect when only log4j and reload4j are candidates and then explicitly prefer reload4j, but let things fail otherwise? Or maybe the detection plugin could just let things fail and then the resolution plugin could automatically add such a specific strategy?