Start from the default ruleset when configuring custom rules

[Bazooper-blip]

Addresses the core request in #80: switching to "Use a custom ruleset" in the Standalone Mode settings now starts from SonarDelphi's default ruleset instead of selecting every rule, so the default set can be fine-tuned by adding/removing rules.

Changes:

• Server: RemoteRule and the rule-retrieval response (RuleData) carry a defaultEnabled flag. Standalone hosts populate it from SonarLintRuleDefinition.isActiveByDefault() — the same source already used to decide the default-ruleset analysis behaviour. Rules from a SonarQube server report true, since everything retrieved there belongs to the active quality profile (the flag is only consumed by the standalone settings UI).
• Client: TRule parses the new optional defaultEnabled field (defaulting to false for older servers).
• Settings UI: when the rule checklist is populated and no custom ruleset has ever been configured (saved settings are "use default ruleset" with no disabled-rules list), the checklist is initialised from the default ruleset. An existing custom selection is preserved exactly as before, and "Enable all"/"Disable all" still work.

The follow-up suggestions in the issue's comments (a search bar and friendlier list ordering) are not included — they're UI work that seems better as a separate change.

Testing: server Maven suite passes; client suite passes with a new TRule.CreateFromJson test for defaultEnabled (present and absent). The settings-frame behaviour compiles and follows the existing populate/save flow, but I could not exercise the dialog in a live IDE — a manual check of switching between default/custom rulesets before merge would be appreciated.