Display DokuWiki's line breaks (\\) as real line breaks (\n).

I've been using this plugin for a while now and it made editing tables indeed a whole lot easier.
However, I often had to use tables with line breaks inside of cells which quickly started to look confusing because I couldn't just use Alt+Enter or Strg+Enter (which both did insert a real line break but broke the table syntax since you can't use real line breaks in table cells). Instead, I had to use \\ .
Recently I had to port very complex table to DokuWiki and so I decided to modify this plugin to make editing such tables easier.

So this commit does the following:
- In the editor, DokuWiki line breaks (\\ ) are displayed as real line breaks (\n)
- If you insert a DokuWiki line break, it is converted to a real line break when you leave the cell
- If you use Alt+Enter / Strg+Enter to insert a real line break, the table syntax doesn't break anymore since upon saving all line breaks are converted to DokuWiki's line breaks

If you need a demo, just let me know and I'll set up a DokuWiki with the modified plugin.