Update Gradle, update dependencies, update Java

[voidowl-rl]

Gradle: 3.5 -> 6.3
Java: 8 -> 14
Slf4J: 1.7.25 -> 1.7.30
Logback: 1.2.2 -> 1.2.3
Janino: 3.0.7 -> 3.1.2
Nifty: 1.4.2 -> 1.4.3

Bundled JDK: Must be switched from OracleJDK to OpenJDK.

PMD: Removed targetComp Java 1.7

[KayMD]

Illadownload does not compile
Error: --module-path requires module path specification

[KayMD]

Current plan is that we will merge dev to master, then merge this to dev with downloader/intall4j updates (see: https://github.com/KayMD/Illarion-Java/tree/updated-install4j) after the release client update.

[vilarion]

Quick fix, probably incorrect, but lets me run the client (yay). You can use it to fix it faster and better: 0001-Crudely-fix-compiler-errors.patch.txt

[eduardorm-dev]

Hello, are there any plans to come back to this issue?
In my case, when trying to build the project (with IntelliJ from 2024), it prompted me to update to at least Gradle 4.5 (and recommended 8.10). Changing to 4.5 or some other version requires a minimal change of configuration, no need to touch the source code.