Error in run.sh for running CQ-editor

In `doc/installation.rst`, under the CQ-editor installation instructions, it says
```
To run from command.:

$HOME/cq-editor/run.sh
```
However if you try and run this command while not already inside the cq-editor directory, it fails.
```
birdpet@earth:~$ $HOME/cq-editor/run.sh

/home/birdpet/cq-editor/run.sh: 2: exec: bin/cq-editor: not found
```
`run.sh` runs `exec bin/cq-editor`, which is relative to the user's current directory, rather than the directory of the script. Either the documentation should be changed to tell users to first cd into the directory, or the contents of run.sh should be changed to something like the following:
```
#!/bin/bash
parent_path=$( cd "$(dirname "${BASH_SOURCE[0]}")" ; pwd -P )

cd "$parent_path"
exec bin/cq-editor
```