No useless configure calls, namespace handling,  base and conf paths, no flag images

Through calling the first `init()` of plugins at the right time, we were able to get rid of all duplicate `configure()` calls we had to do on startup. This also makes the presence of `configure()` obsolete to some degree, as this code could reside now completely inside the `init()` but it's probably still ok to have it for stylistic reasons.

This adds code pieces that allow to describe the workflow outlined in the soon to be released `guides`. Angular `values` are used to define the default `CONF_PATH` as well as the `BASE_PATH`. This makes it very easy to use `Arethusa` code outside of its main repository without introducing breakage due to relative file paths and is a pre-requisite for its use as a `bower` package (cf. #388).

Note that the widget demo we did a while ago might be out of sync because of that. We'll have to deal with this soon again anyway.

The `flags` directory has been gone - the tiny images are replaced by encoded strings we serve right through our scss/css.

A minor fix for the nestedMenuCollection, that behaves bad with really long lists is also included.



Closes #355 
Works on #384 
Might temporarily break our work on #325
Temporary fix for #384