New Post page: Put Preview button back on the left.

There was a recent regression due to "float: right".
Center text input form elements in all 3 cases: New Post, SPV comment, excerpt comment.
for DM notifs @actors only holds one name
Remove superfluous centered-contents CSS class.
synchronise es_ES translation
synchronise es_SV translation
synchronise fr_FR translation
synchronise hu_HU translation
synchronise it_IT translation
synchronise de_DE translation
Revert mistaken commit of _host.
use help_bubble helper
wrap in paragraphs instead of using <br/>
fix msgid
fix: `rivers` is an array, not a string
Merge pull request #33 from Libertree/fix-post-and-comment-form-buttons

Fix post and comment form buttons
use colour scheme: main_green = leaf
dust colour for detached comment window
dust colour for chat tabs
colour pool windows according to colour scheme