New look + Mandriva binaries

I've finally managed to implement a change that I meant to do for a while: restructuring the labels and the use of colors. This is supposed to downgrade the labeling system from "hopelessly confusing" to merely "confusing". So:

1) The 1-letter labels got replaced with 2-letter ones, where the first letter is used to identify the group, while the second letter is for the place of a note inside its group.

2) The background color of a note no longer depends on its severity (error / warning / support.) Instead, only the labels use different colors.

3) Gradients are used for easier easier visual identification of note groups.

4) In the Configuration dialog there is a new tab, where the background colors can be changed for each group. (Note the possibility of using "custom colors", for a more consistent look.)

5) The tag editor's background colors can be configured from its Palette dialog.


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Other changes:

- Changes that are made by external tools are now detected and the user is told to reload. (Previously the program would just crash.)

- The font that is used for labels in the main table can be made smaller, so the note columns take up less space.

- Tooltips for the main table's header contain note descriptions.

- There are now Mandriva binaries available.

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(Note that the documentation has not been updated yet, to reflect these changes.)