Additional caches

[tobiasschweizer]

• get user by username
• get project by shortcode
• get project members by shortcode
• get groups
• get users

closes #106

[tobiasschweizer]

@kilchenmann I have just realized that the generic cache I wrote does not work for getting project members by project shortcode because the MembersResponse does not have an id.

Also I have realized that the generic cache requires an item to be identified by one id, but users and projects can be identified in three different ways. Of course we could have a separate cache for each way of getting a user, but there would be redundancy.

[kilchenmann]

I have just realized that the generic cache I wrote does not work for getting project members by project shortcode because the MembersResponse does not have an id.

I handled it with a key for the cache like 'members_of_' + this.projectcode. But it's ok. I will optimize and use my generic cache service in the app itself. No problem...