Replace native GNU readline with JLine (#5)

[cansin]

Replace native GNU readline with JLine

Closes #5.

Motivation

USE's interactive command line relied on the native Unix GNU readline
library via a JNI binding (GNUReadline + natGNUReadline.c). This required a
platform-dependent native compilation step as part of the build and was
effectively unavailable on Windows, so most users silently fell back to a bare
input stream with no line editing or history.

This PR replaces that with the pure-Java JLine
library — which was already declared as a dependency but never wired up —
giving line editing and a persistent command history on Linux, macOS and
Windows with no native build steps.

What changed

• New JLineReadline — a Readline implementation backed by JLine's
  ConsoleReader with a FileHistory. History expansion is disabled so the
  SOIL ! / !! commands are passed through verbatim.
• LineInput.getUserInputReadline() now returns the JLine implementation
  for interactive terminals and falls back to the existing StreamReadline
  when no console is available (piped/headless), preserving current
  non-interactive behaviour.
• Removed the JNI GNUReadline class and the natGNUReadline.c native
  source, and the System.loadLibrary call; declared the jline module in
  module-info.
• Dropped the obsolete "GNU readline not available" warning from the shell.
  The -nr command-line switch is kept as an accepted no-op for backward
  compatibility (it is still passed by the Windows launcher and the integration
  tests, and unknown flags abort startup).
• Docs & scripts: updated INSTALL, README, and NEWS; removed the
  native-only LD_LIBRARY_PATH from bin/use and the now-obsolete -nr from
  bin/start_use.bat.

Behaviour & compatibility

• Interactive terminals gain bash/emacs-style line editing and history
  (~/.use_history) on all platforms.
• Non-interactive/piped input is unchanged (StreamReadline).
• No native toolchain is required to build USE anymore.
• No new dependency is introduced — jline:jline:2.14.6 was already on the
  classpath.

Testing

Developed test-first (red → green) with a regression safety net:

1. Added characterization tests for the existing StreamReadline / LineInput
   behaviour and confirmed they pass against the current implementation.
2. Added JLineReadlineTest and a LineInput factory test for the new
   behaviour (red before the change).
3. Implemented the migration; all of the above pass (green).

Verified locally:

• use-core unit tests: green
• use-gui unit tests: green
• ShellIT end-to-end shell integration suite: 129 tests, 0 failures
  (exercises real command files in-process and confirms -nr still works)

[ichxorya]

Very nice, I would love to review this asap. I also found this problem while working on my PR, which I hadn't fixed due to not relevant to the PR itself.