Minor UI fixes and improvements

[joulei]

• [x] Gray out icons of not yet implemented features

• [x] Minor vertical mis-alignment on small state items

• [x] Missing/squashed left padding on user profile sliding pane

• [x] Misaligned code block background, miscellaneous vertical spacing issues

• [x] Change the hover bg color for Message to have starker contrast with background color of Html blocks (draw_block: { quote_bg_color: ... })

• [x] Text input's text is invisible due to color matching the background

• [x] Update user profile colors to match the general UI theme

• [x] Change text color in html block bg in RoomPreviewSelected, to MESSAGE_TEXT_COLOR

• [x] Make rooms list sidebar narrower

• [ ] Make the border between the "replying preview" and the bottom of the timeline view more distinct, either via a shadow or different bg colors

• Display the message timestamp next to username. Edit: this will be worked on separately.

[kevinaboos]

Need to fix the color of the html quote block bg in the RoomPreviewSelected:

here's an example of it unselected:

and here it is when selected -- it's white text on a near-white bg