Another one of those MR that fixes many many small-to-medium things

• Fixes #92 (closed) and maybe-fixes bugs where likes counter showing more likes than there is really.
• Improves on !308 (merged) : makes tab-switcher a reusable component, adds styles to make tabs look like tabs and not like buttons.
• Fixes StillImage: maintain aspect ratio of <canvas> (no more stretching), fixed canvas rendering with 1,1 offset, made canvas render at image's original resoultion.
• Fixes favorite button jumping places because retweet button being hidden for FO/DM posts. Now lock icon with alt-text explaining the reason why it's so is shown
• Fixes #75 (closed)
• (Partially) fixes #122 (closed)
• Cleans up some styles in panels, decreased padding in panel's title to be more inline with content, moved unseen-counter to be after title to make it less jumpy.
• Fixes #52 (closed)
• Fixes #72 (closed)
• Fixes #87 (closed)
• Adds optional ability to have logo in navbar to follow color scheme of the theme, so no more white-on-white logo.png. Uses CSS masks which are not available in some browsers (IE11, Edge) in those cases it falls back to displaying image (check is done via JS because @supports css media query itself isn't... supported everywhere). This requires image to be monochromatic and basically just uses alpha channel of it. Also works with SVGs. For instances that have colored logo (i.e. CRT) added config option for disabling this feature logoMask: false (default: true)
• Added option to adjust space between logo and navbar, logoMargin, it's a CSS length-value with units. So that admins don't have to change image itself and can just crop image to save on traffic/load times (sweet jesus fuck, CRT's logo is HUGE (in dimensions)).
• Changed section related to staticConfig and apiConfig - instead of using likes of apiConfig.stuff || staticConfig.stuff which will cause problems like apiConfig.stuff = false || staticConfig.stuff = true ==> true instead using Object.assign to combine both objects and use that instead.