Create new index

[jsbien]

Let's imagine the following scenario: I'm just looking for something without an index open. Unexpectedly I see something interesting and want to take a note of it, the most natural way being an entry in an index. However at the moment to create a new index one has first create an empty index with another tool.

[Michał Rudolf]

Create new index. Closes #281

→ <<cset 59824ad66832>>