Merge pull request #23 from pgerdt/localtime-link

[timed] Change location of time zone link that timed manages
Fix compilation when log level >= LOG_DEBUG
Use statefs to manage context properties in Qt5 version

Centralize context property handling to class timed.
The context properties /com/nokia/time/time_zone/oracle
and /com/nokia/time/system_time/operational appear to
be obsolete, so they have not been ported to Qt5.
Merge pull request #24 from pgerdt/statefs

Use statefs to manage context properties in Qt5 version
[timed] Do not link to time zone information in post install

Time zone may be set during image creation by copying a file
from /usr/share/zoneinfo to /etc/localtime. If the link chain
/etc/localtime -> /var/lib/timed/localtime -> /usr/share/zoneinfo/<file>
exists, then <file> in /usr/share/zoneinfo/<file> will be
overwritten.

Set the UTC time zone as the default timed time zone by
copying /usr/share/zoneinfo/UTC to /var/lib/timed/localtime
during post install. Overwriting /etc/localtime will then
not overwrite files in /usr/share/zoneinfo.

Timed changes the file in /var/lib/timed/localtime into a link
while setting the time zone during runtime, see
source_settings::fix_etc_localtime().
[timed] Do not remove time zone link if target does not exist

If the time zone that timed is trying to set does not exist
in directory /usr/share/zoneinfo, then do not remove the existing
link /var/lib/timed/localtime -> usr/share/zoneinfo/<file>.