Plugins screen improvements

[amadare42]

Refactoring & plugin screen improvements.

General

• HunterPie.TestsCore -> HunterPie.Core (.net framework)
• Added "garbage collect" button to debug tab
• fixed settings tab isn't populating when they're created before SettingsControl initialization

Plugin Screen

• cosmetic & layout changes
  • subtext now spans below control buttons to fit information better
  • added collapsible plugin card (e.g. plugin preview header)
  • Installed plugins section is always visible (so busy indicatory will be visible on application start)
  • changed default list/readme columns ratio and min widths
  • changed "Open plugins directory" icon
• readme improvements
  • image caching (see below)
  • show/hide sections
    • this commented block will be displayed as part of readme

      <!--<include>
      some content
      </include>-->

    • this block will be hidden in app readme:

      <!--<hide>-->
      some content
      <!--</hide>-->

• added cache for readme images and plugin icon
  • app will search icon in this order: <plugin_dir>/icon.png, <plugin_dir>/.cache/icon.png, registry
  • all readme images will be cached in <plugin_dir>/.cache directory (ignoring svg files)
• added plugin actions
  • format:

    "Links": [
    "ICON_NAME|button name|http://example.com", 
    "ICON_NAME|http://example.com", 
    "http://example.com"
    ]

  • some data will be resolved automatically:
    • if link lead to github, it's icon will be selected and "homepage" name will be used
    • if link lead to discord, it's icon will be selected and "Discord" name will be used
    • if link is unknown, link icon will be used
    • if no link is posted, but readme leads to github.com (or githubusercontent.com), repository root will be used as home page
  • custom links support
• added plugin release date information
• fixed disposing of plugin ViewModels (should fix memory leak)
• re-use HttpClient more to reduce resources usage
• removed plugin installation reporting in debug mode

Infrastructure

• added AlignableWrapPanel that aligns it's children at center
• FlatButton added icon binding (previous implementation wasn't working for non-static resources)
• added typed RelayCommand

Further improvements

• readme doesn't support svg
• readme doesn't support tables (since we're using markdig's xaml renderer instead of wpf one)