Load SQL Drivers using isolated ClassLoader

[bivashy]

Pull Request Etiquette

• I have checked the PRs for upcoming features/bug fixes.

Changes

• Internal code
• API (affecting end-user code)
• Other: _____

Closes Issue: #153

Description

This Pull Request loads DatabaseHelper and JDBC driver using custom ClassLoader instead of loading directly into AuthPlugin class loader.
Current state: Done

[bivashy]

Plugin now uses ServiceLoader#load(Class<T>, ClassLoader) and loading into the IsolatedClassLoader instead of plugin ClassLoader.
Other plugins cannot have access to the database driver directly, and it doesn't interfere if they are properly relocating, or else loading isolated.