Improve config.js consistency

[lejoe]

While refactoring the way the config.js is built, we identified a possible improvement.
We're not too happy about the fact that we need the entryPaths variable.

The main reason lays behind the fact that we have languages. That modifies the path and those entrypoints become dynamic

We might explore into transforming the config into functions.
Here are a few possible apis:

config.getEntry('scripts')
config.getWatch('scripts')
config.getEntry('styles')
config.getWatch('styles')
config.getEntry('content', 'de')
config.getWatch('content', 'de')

---

config.scripts('getEntry')
config.scripts('getWatch')
config.styles('getEntry')
config.styles('getWatch')
config.content('getEntry', 'de')
config.content('getWatch', 'de')

---

config.scripts.getEntry()
config.scripts.getWatch()
config.styles.getEntry()
config.styles.getWatch()
config.content.getEntry('de')
config.content.getWatch('de')

---

config.scripts('getEntry')
config.scripts('getWatch')
config.styles('getEntry')
config.styles('getWatch')
config.content('getEntry', 'de')
config.content('getWatch', 'de')