Debian: Merge back release packaging into development

Signed-off-by: Markus Frosch <markus@lazyfrosch.de>

Refs #5816
Debian: update changelog to warn about package base
Plugins: add fping4/6 commands

refs #6225
Documentation: fix ssh example
Notifications: Check if disabled when sending reminder

refs #6510
Fix: Icinga doesn't send SetLogPosition messages when one of the endpoints fails to connect

fixes #6537
Add missing license headers

refs #6493
Cache parent and child object for dependencies

fixes #6565
Fix Livestatus queries where the second operand is omitted

fixes #6494
Disable console log after activating all config items

fixes #6316
Adding ports to checks pop/imap/smtp and new check dig

fixes #6531

Signed-off-by: Gunnar Beutner <gunnar.beutner@netways.de>
add new cmake option INSTALL_SYSTEMD_SERVICE_AND_INITSCRIPT requested for Gentoo packaging

fixes #6498

Signed-off-by: Gunnar Beutner <gunnar.beutner@netways.de>
Improve the systemd service definition file

- put "Icinga" back in the "Description=" field as usually only the description is displayed on unit start/stop or shown in syslog
- add dependency to carbon-cache.service
(systemd only cares about dependencies if the respective services are enabled, so this does not hurt if someone does not have carbon-cache
installed at all or is not using it at the moment)

fixes #6551

Signed-off-by: Gunnar Beutner <gunnar.beutner@netways.de>
Update AUTHORS
Remove source line information from stacktraces

fixes #6576
Fix PostgreSQL warnings about escaped strings

fixes #5577
Replace FindMYSQL.cmake with another script which has a compatible license

fixes #6493
Fix support for the Check_MK frontend

fixes #5312
Build fix for Debian unstable

refs #5312
Adapt url_cgi_path in cgi.cfg, so that icinga2-classic doesn't trigger csrf protection