Ddc errors view

[devoncarew]

A fancy new errors view:

this:

• replaces the default linter error panel with a new custom errors view for dart
• errors and warnings focus on the currently active project
• there's a terse summary on the status line; infos levels issues are not summaries there, just errors and warnings
• clicking on the status line will toggle the error view
• issues are sorted by severity and then file path
• users can change to and from the new and old views in the settings
• the view is a set size and is adjustable by the user; it will not obscure text while the user types