Plugin

Allow passing a search query to the running instance via the command line.

Using `zeal --query 'java|Hash'` will open a zeal window with a search for `java|Hash`. If an instance of zeal is already running it will be brought to front with the query and the first result highlighted. Otherwise a new instance will be started.

**NOTE** 

The purpose of this is to allow for easy integration of `zeal` into existing plugins for Dash. Therefore this pull request also includes a change of the delimiter character used to filter docsets, from a pipe character `|` to the Dash convention of a colon `:`.

This change should mean an out of the box compatibility with Dash plugin syntax (`docset:query`).