Fix the mess with main and addon.

[Edward_Lii]

Hello all,

There are currently two groups of content: main and addon.
The difference between the two is that the one is located in the datadir and the other in the user path.
But for the rest they are the same, which isn't good in my opinion.

Here is the current situation:
Main:

Where: datadir
Editable: [√]
From where: installation

Addon:

Where: user path
Editable: [√]
From where: addon manager

Users can change levels from the main group using the leveleditor, or change the default levelpack using the levelpack editor.
This shouldn't be possible (from inside the game), the main is for default static content.

The second problem is that installed addons can also be changed using the leveleditor.
This means a user can ruin the addon from within the game.

In order to solve these problems there should be a third group, custom:
Main:

Where: datadir
Editable: [X]
From where: installation

Addon:

Where: user path
Editable: [X]
From where: addon manager

Custom:

Where: user path
Editable: [√]
From where: user made

The selection of the different content types should become.
Themes: Stays the same, one single line list box listing the themes from all three groups.
Or just two groups since there's no way for the user to create themes from within the game.
Levelpacks: Single line listbox in the levelselect screen that list levelpacks from all three groups.
Levels: A filedialog with two searchpaths, one is a combination of the main and addon group, the other lists the user group.
Or three different searchpaths?

It will still be possible to load levels from any group in the leveleditor, but not save to them.

Any feedback is welcome!