Saving user preferences

Allows to persist settings through `localStorage`, so that a user can re-enter the application and find the environment in the same state as when he left.

Reading from localStorage is done in the `configurator` in the `delegateConf` function. So everything that obtains its configuration/settings through it, can immediately participate in this.

Writing is done in two places: the `pluginSetting` directive and the default action handling in `globalSettings`. What's NOT included so far is when in `globalSettings.defineSetting` a custom directive is defined - but right now it's probably good not to persist such settings anyway (e.g. the layout, because the availability of a layout depends on the app configuration).