[FR]: Extensive "Custom skin colours" options

[RetroAbstract]

Brief description of the feature request

Following the additional options I added on the "4 additional options in "Custom skin colours"" FR, I decided to close that issue and open this one.

Ultimately the end goal, on top of the already customizable files in a skin's folder, and existing options already in "Custom skin colours", would be to have the same options in the "Custom skin colours" as the "Colors" tab in the "Fonts & Colors" menu QuiteRSS has (excluding those where no visible changes were noticed when tweaking - see list below*) and more, allowing the user to fine tune the colours of many elements of RSS Guard directly within the program:

*Equivalents of QuiteRSS "Colors" options to RSS Guard:

Feeds list color = Feed title text colour Feeds list background = Feed list base(1) colour News list color = Read articles title text colour News list background = Article list base colour Focused news color = No visible changes when tweaking this one Focused news background color = No visible changes when tweaking this one Link color = Link text colour in message viewer/article previewer & internal browser Title color = Article title text colour in article list Date color = Article date text colour in article list Author color = Article author text colour in article list News text color = Message viewer/article previewer & internal browser text colour News title background = Message viewer/article previewer toolbar colour News background = Article previewer & internal browser base colour Feed with new news = Feed title text colour with new articles (upon fetching) Count of unread news in feeds tree = Colour of unread news count in feed list Text color of new news = New unread articles title text colour (upon fetching) Text color of unread news = Unread articles title text colour Focused feed color = No visible changes when tweaking this one Focused feed background color = No visible changes when tweaking this one Disabled feed = Disabled feed title text color Alternating row colors = Alternate row colour in article list Notification text color = No equivalent as QuiteRSS uses it's own notification system Notification background color = No equivalent as QuiteRSS uses it's own notification system

Additionaly, on top of the QuiteRSS "Colors" options, the following would be great too:

• "Highlight colour" option ("ToolTipText" in skin metadata file)
• "Highlight text colour" option ("HighlightText" in skin metadata file)
• "Button area colour" ("Button" in skin metadata file / see screenshot below(2))
• "Button area text colour" ("ButtonText" in skin metadata file)
• "Window area colour" ("Window" in skin metadata file / see screenshot below(3))
• "Window area text colour" ("WindowText" in skin metadata file)
• "Feed with unread articles title text colour"
• "Feed category with unread articles title text colour"
• "Status bar loading bar colour"
• "Status bar text colour"

(1)"Base" is the background colour. The options from QuiteRSS allow the user to apply different background colours to different lists (For example a blue feed list background colour, a red article list background colour & a green message viewer/article previewer background colour).

(2)"Button" zone highlighted in yellow (not visible in screenshot but also includes the feed list's, article list's & the message viewer/article previewer's scroll bars aswell as the message viewer/article previewer toolbars and the contours of the elements' logos in "View > Show/Hide"):

(3)"Window" zones highlighted in yellow: