doc: update links to git repositories (savannah -> github)
de.po: update german translation
doc: update German auto-generated files
rmodifier: remove plugin (replaced by trigger)
trigger: add some missing "+" after spaces in regex of default triggers cmd_pass/msg_auth
core: save and restore mute state in command /mute (bug #41748)
core: mute all buffers by default in command /mute (replace option -all by -core)
debian: replace rmodifier by trigger in control file
trigger: update description of trigger plugin
Use asciidoc file ending for all asciidoc files
core: add "foreign" for AM_INIT_AUTOMAKE to ignore missing files and remove some warnings
core: add .asciidoc files in main Makefile.am
core: add link to formatted version of {ChangeLog|NEWS}.asciidoc
relay: add signals "relay_client_xxx" for client status changes (closes #2)

New signals:
- relay_client_connecting
- relay_client_waiting_auth
- relay_client_connected
- relay_client_auth_failed
- relay_client_disconnected
relay: add info "relay_client_count" with optional status name as argument

Use in evaluated strings (for example in /eval or triggers):
- "${info:relay_client_count}": total number of relay clients (any status)

With a specific status:
- "${info:relay_client_count,connecting}"
- "${info:relay_client_count,waiting_auth}"
- "${info:relay_client_count,connected}"
- "${info:relay_client_count,auth_failed}"
- "${info:relay_client_count,disconnected}"
core: rename file NEWS.asciidoc to ReleaseNotes.asciidoc
core: move content of INSTALL.asciidoc into README.asciidoc
core: add file Contributing.asciidoc
core: fix typo in Contributing.asciidoc
core: add sub-sections and note about scripts in Contributing.asciidoc