Move http repository access to /r/$project

It's a shorter URL and also helps git derive the right name
for the clone.
Stylistic fixes
Use new semantics for adding an stdin stream to PassThru
If necessary, create git repository on first http access
Document HTTP repository access for git
Use REDIRECT_* for FastCGI/PHP Authorization handling
Make HTTP auth cover all popular FastCGI workarounds
Use idf_exec_prefix when git tools are called
Write-protect git repository over HTTP!

I totally misunderstood the access control mechanism (but it's logical
that it behaves the way it does), and so on git projects with "open"
source access, repos were write-for-all.

This should fix it by enforcing member-or-owner auth for writes.

Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
The beginnings of issue due date notification functionality
The beginnings of issue due date notification functionality
Merge branch 'feature.issue-due-date-notifications' into develop
fix merge conflicts