Made links relative for GitHub compatibility.

Made links relative for GitHub compatibility.

This fixes a regression caused by a change in CouchDB4J 0.8 introduced
in commit 1eaebde0. CouchDB4J 0.8+
always defaults to `reduce=false` as long as grouping is not enabled.

This fixes a critical bug introduced in commit
1eaebde0 which lead to premature
deletion of guest sessions caused by incorrect type handling.

Always set `creationTime` on session creation. Sessions with invalid
timestamps might otherwise be deleted by the scheduled cleanup.

Fix NPEs

See merge request !73

Fixes a regression introduced with commit
dd749370.

Refs arsnova#85
Refs !16

Fixes a regression introduced with commit
d74ef999.

Refs arsnova#85
Refs !25

Fixes a regression introduced with commit
7207bad9.

Fixes arsnova#84

This fixes compatibility with CouchDB 2.

The Netty version set by Spring IO platform's BOM is not compatible with
netty-socketio.

Our version of CouchDB4J has been updated to fix and improve type
handling for database keys. Strings are no longer converted implicitly
to integers or booleans based on their content. This lead to bugs if key
and property values were compared.

Use relative links to repository files in documentation

See merge request !64

Also block local access using IPv6

See merge request !63

Rename CI repository variable for GitLab 9.0+

See merge request !62