Simplify API documentation

[narnaud]

This is a follow up of #49

Now that we only have a Script module, it doesn't really make sense to explicitly says it's in this module.

• Remove all \inqmlmodule Script in the code documentation
• Change cpp2doc tool to always put in the Script module if there are no \inqmlmodule (we want to be able to use it, just in case for later)

[narnaud]

Probably need to do #56 first, so we don't have to change the module name again.

[LeonMatthesKDAB]

Note: #56 is done now.