Support standalone mode rule configuration

[fourls]

This PR adds a new user-level configuration setting to configure which rules are applied in standalone mode:

By default, DelphiLint is configured to use SonarDelphi's default ruleset (the Sonar way profile), preserving existing behaviour. Users can opt-in to configure their own ruleset, at which point they can enable or disable which rules they like. Under the hood, only disabled rules are stored, meaning that any new rules that appear as a result of a SonarDelphi upgrade will be automatically enabled.

As tends to happen with these sorts of paradigm-shift changes, this PR also includes a few collateral improvements:

• Some Sonar issues have been fixed
• The settings form has been redesigned as a tabbed view
• SonarDelphi version configuration now only queries GitHub when a new "Edit" button is clicked, rather than upon form show
• SonarDelphi version configuration now queries GitHub in a background thread
• Rule retrieval in Standalone Mode now includes security hotspots and excludes template rules
• The SonarHostTokens settings item is no longer capped at 2048 characters

Fixes #16

[fourls]

Implemented compatibility with the new features in the VS Code companion - while you can't customise the rules from within VSCode, it will honour the disabled rules configuration.