New user preference: open new tasks in edit mode

Adds a new checkbox user preference to Settings > Settings > Misc: "Open new tasks in edit mode".

When this preference is enabled, new tasks the user adds using the Web form will open expanded, with all options visible and ready for editing, instead of the current behavior where the task saves with defaults and requires an additional click or double-click to access extended options.

Meant for power users who like to tweak tags, difficulty, attributes, etc. for most tasks they add, so this defaults to `false`.