config: more details, link to new docs section

and rename doc/Changelog to doc/CHANGELOG
LConf.spec: add doc/CHANGELOG
SlaveSync: allow icinga perfdata* dirs and command pipe to be set through configure

fixes #1864
LConfSlaveSync: add configure options for pidfile and debug log

fixes #2090
add make-tarball script, and make create-tarball option

fixes #2092
LConf.spec: use slavesync configure options, correct temp dir
doc/CHANGELOG: revamp CHANGES section for release