* fix for "Open" tab placeholders in FireFox
this PR fixes the placeholders in FireFox not being removed on drag-leave from time to time
it consists of 2 mods where apparently both are needed:
- creating a `droppable-item` macro where whitespace is trimmed. that macro contains the droppable and inserts the placeholders
- removing the ` ` entity in favor of an inline style `height:2em;` on the placeholder div, putting it in a macro where whitespace can be trimmed, too
I'm investigating if there's a similar fix for the top page dropzone
* remove unnecessary whitespace trim, add css classes
`.tc-sidebar-tab-open-item { position: relative; }`
`.tc-sidebar-tab-open .tc-droppable-placeholer { line-height:2em; height:2em; } `
* replace times entity with close-button
* add sidebar-open-tab styles
Fixes#82.
The old behaviour was to parse the content of a widget or html element
in block mode if the opening tag was followed by a line break. The new
behaviour requires two line breaks.
This makes it possible to include linebreaks more liberally within
wikitext, although care must still be taken to only use double line
breaks when the block mode behaviour is desired.
The code change here is very simple, just a single line change in
html.js. Most of the other changes are to convert various single line
breaks into double line breaks.
