scape modloadmsg

when you use something like this in a easyconfig, you need to scape $

```
modloadmsg = """To list all the available utilities execute ls \\$EBROOTPICARD"""
```

With this fix easybuild will take care of scaping 

This looks like an easy fix, but I don't think it's the correct one in this case... 

For example:

```python
re.escape("This. is $just a ^test [](*)")
'This\\.\\ is\\ \\$just\\ a\\ \\^test\\ \\[\\]\\(\\*\\)'
```

For a string like `"This. is $just a ^test [](*)"`, only the `$` needs to be escaped as far as I know, since that's the only character with special meaning in a module file. 

It think the correct fix is this:

```python
# escape any '$' characters which indicate variables in module file
re.sub('\$', r'\\$', msg)
```

See for example:

```python
re.sub('\$', r'\\$', "This. is $just a ^test [](*)")
'This. is \\$just a ^test [](*)'
```

Thoughts @pescobar?