[3591] logger_unittest_support no longer overwrites KEA_LOCKFILE_DIR_FROM_BUILD
[3591] Logging initialization cleaned up
[3591] Logging variables simplified

 - KEA_LOCKFILE_DIR_FROM_BUILD renamed to KEA_LOCKFILE_DIR.
 - KEA_FROM_BUILD_LOCALSTATEDIR, KEA_LOCKFILE_DIR_FROM_BUILD removed
 - It is possible to disable lockfile now
[3591] Print error to stderr after failing lock file creation.
[3591] Default logging refactored.
[3591] Unit-tests for new variables implemented.
[3591] Documentation updated.
[3591] Unnecessary variable set removed.
[3536] Logging section in User's Guide updated.
[3536] logging example in kea.conf in keactrl fixed
[3591] Fix for DESTDIR installation hook
[3536] Missing coma added.
[3591] Small edits of logging documentation during review.
[3536] Changes after review:

 - Logging section updated.
 - Missing coma in kea.conf.pre added
 - ${localstatedir}/log is now created
Merge branch 'trac3536' of ssh://git.kea.isc.org/git/kea into trac3536
[3536] Disabled ddns in keactrl.conf.in
[3591] Shell tests renamed.
[3591] Logging::applyDefaultConfiguration() removed.
[3536] Fixed a few editorial nits.
[3591] Changes after review:

 - ChangeLog updated
 - applyDefaultConfiguration() removed
 - couple unit-tests renamed
 - comments added for code that uses TEST_DATA_TOPBUILDDIR
 - copyright years updated
 - one function moved: logger_unittest_support.cc => logger_support.cc