Added `AddPackage` and `RemovePackage` methods (#166).
Updated outline to use `AddPackage` method (#337).
Updated code based on static analysis suggestions.
Updated `AddPackage` to assign package file name (#166).
Updated handling of extensions to allow more symbols in extensions.
Added hiding/showing files by type in the project/filetree (closes #375).
Added marking file after showing files in the tree (#375).
Fixed not hiding directories when files without extension are hidden (#375).