Implementation of showSource option

[kevin-frugier]

The pages http://grunt-docular.com/documentation/docular/docularconfigure/groups (404 when navigating directly and not from index btw) or https://github.com/Vertafore/docular/blob/master/lib/scripts/docs/configure/configure.md
states the following :

showSource – {boolean} –
Defaults to false. When true will copy all source files to the webapp so they can be displayed in the UI. WARNING All files within this group should be considered public. All information should be considered insecure. Note, you can set the 'showSource' configuration at the section level to override the group level setting

However, when we look at the original code of docular, at least at commit 567d35d we don't see it being used.
The code copies all source files and the angular template always has the showSource button enabled.

Maybe the feature was implemented in the past and removed at some point. But I find it very handy.
I have therefore prepared a code change where the showSource option is inherited (if not defined) and properly used both during copy of the source files to the "sources" folder and also taken care of properly in the angular template.