Log level colors can be picked, saved and restored

[Kittyfisto]

Changes for users:

• Introduced settings to save & restore log level colors (foreground & background)
• Introduced toggle-button to display/hide "other" log lines (i.e. those which could not be matched to a log level known by Tailviewer)
• Selecting a white or transparent background color causes Tailviewer to fallback to its alternating row color scheme of FFFFFF/E8F1F7; Otherwise only the selected color is used as a background color
• Removed line hover effect (previously the background color of some log levels was slightly changed if the mouse happened to hover over the line)

Changes for plugin developers:

• Added LevelFlags.Other value
• Changed the meaning of LevelFlags.None: From now on, plugin developers should use LevelFlags.Other where they previously used LevelFlags.None
• Changed LevelFlags.All to include LevelFlags.Other

Changes for TV developers:

• Added dependency to Xceed.Wpf.Toolkit to have a decent color picker

Fixes #216

[BenKenobi85]

The dialoge to let you pick a color follows a weird scheme. Applications typically provided a color palette where the different colors are ordered in a rainbow like fashion. This one IMHO does not follow any obvious rules.

[Kittyfisto]

Thanks for the feedback, it didn't even come to my mind to see if those colors can be re-arranged. I will take a look if it's possible and try to copy a more sensible scheme.

[Kittyfisto]

Found a simple way to have the colors sorted by hue, brightness and saturation (the default was sort alphabetical):