Gallery improvements + Display message when no apps are found

[Taffroi]

APP PANEL

• Now displays a message at the center of the screen when no apps are found
• Category title header is now extrabold and better aligned

Fixed

• Category group headers won't be too big for other themes than adw-gtk3(-dark)

[Taffroi]

I improved the gallery section to make it easier to navigate. The little dots were very annoying to use so I added arrows and I changed the look & feel of the section at the same time.

DETAILS -> GALLERY

• Screenshots now have a FIXED HEIGHT, so the section height will not change when browsing screenshots. I also scaled down a bit the screenshots so they take less place in the details window.

How it looked before when browsing screenshots for certain apps

Here's a screenshot to compare the new height for screenshots. You can see how the description has more space for it.

• Arrows have been added to let users view screenshots easier.
• Their event boxes extend to the side of the window to make them easier to reach.

• I made the screenshots loop instead of being blocked on the first or the last one. I made a variable in the code to disable this behavior if you don't like it.
• Background color is now darker and extends to the sides of the window
• Navigation dots support CSS transitions.
• The active dot is bigger than the others
• When you hover a dot, it will change color to white and get a border.

• Missing image icon has been changed and is now bigger
• When there's only one screenshot, no navigation (arrow, dots) will appear

DETAILS PAGE

• Details window is now taller when opened
• Details headerbar title is now "About (app)"
• No more separators below the main app section

SIDE PANEL

• Updates count will not be visible when no updates are available

Before

After

APP PANEL

• Options button tooltip is now "Manage permissions" as I believe it describes more accurately this button

ABOUT

• Version label changed to 1.0.8