This commit:
- Refactors centered text blocks currently used for placeholders
for empty tables and puts styles for it in separate class -
.centered-text, simply aliasing text-align: center. Which is
furtherly used in this commit.
- Improves applications settings page to use heading actions, moving
"New application" button there, and displaying placeholder "You
have no applications" in place of empty table.
- Improves custom emoji settings page to use heading action
for "Upload" button, making it more easily accessible without
need to scroll through all of the emojis.
- Improves email domain blocks settings page, moving "Add new" to the
heading actions and using placeholder "No e-mail domains currently
blacklisted" instead of showing empty table.
