reduce number of menu items

This is from @andrewgelman, who wants to reduce the number of menu items on the top page in order to focus user search. The plan will require more clicks to get to some things but there will be fewer choices at each stage.

• What should we do about the workshop pages and other "hidden" content?

• Any URLs that go away should forward somewhere reasonable or be replaced with a page to manually follow.

Here's the new plan from @andrewgelman:

Home Page

As is.

Top-level Menu Items

These will be the menu choices on the home page and the targets of the menu items:

• Interfaces
• Documentation
• Issues
• Community

The first three will remain the same.

Community will get a landing page with links to all the previous pages:

• Users list and dev list (was what we called "Community" before)
• Bug Reports & Feature Requests
• Events
• How to Cite & Citations
• Team
• Developer Resources
• Contributions & Supporters

If we can figure it out, it might make sense to have a submenu of some kind. Otherwise, each of the pages will only have the top-level menu items and it'll be a challenge as to how to lay out that community page index, as it'll require a bit of explanation for each item and some scrolling.

What we have now

Thsi is just an outline of the current site (as of this issue submission):

CAPS are menu pages. Bold items have their own web page.

HOME

• what is Stan
• how to get started
• how to donate (remove NuMFOCUS logo and simplify link to contributions)

INTERFACES

• Language
  • RStan, PyStan, ...
• Higher Level
  • RStanArm
  • ShinyStan
• Lower Level
  • Math library
  • Stan library
• Useful tools
  • Loo
  • Bayesplot
  • rstantools

DOCS

• Manual
• Example Models
• Case Studies
• Tutorials
  • video
  • web tutorials
  • papers
  • books

ISSUES

• Bug Reports
• Feature Requests
• Submit fixes

EVENTS

• meetups
• talks
• courses
• cons

COMMUNITY

• users group
• dev group

CITE

• How to cite Stan
• Books about Stan
• Boosks with examples translated to Stan
• Papers about Stan
• Papers using Stan
• Theses using Stan
• Papers using NUTS
• Software using Stan
• Software using NUTS

TEAM

• Core Developers
• Alum developers

DEVELOP

• suggest or discuss code patches
• contribute code patches
• to do list and projects
• how to join the dev team
• source repos

SHOP

• US shop
• UK shop

SUPPORT

• Contribute to Stan
• Donors
• R&D grants
• Industrial consulting

We also have a hidden page that doesn't have a menu item or any links to it from the site:

Workshops

• birds
• icl_epi
• ...

Beginne damit, die aktuelle Navigation der Website und die im Issue aufgeführten Seitengruppen zu überprüfen, einschließlich Community und der ausgeblendeten Workshops-Seiten. Entscheide, wie das vorgeschlagene Menü der obersten Ebene auf bestehende Seiten abgebildet wird, und prüfe URLs, die entfernt würden. Erledigt ist die Aufgabe, wenn die reduzierte Navigation implementiert ist, ausgeblendete Inhalte berücksichtigt sind und betroffene URLs ein sinnvolles Ziel haben.