Added in officecfg five new properties to be able to set
cache lifetime if needed.

The new properties are available in advanced, expert configuration only,
in org.openoffice.Inet.Settings.

Default values are as follows (value is in seconds):
    OptsCacheLifeImplWeb = 300
        when the web resource is Web only, implementing OPTIONS.
        Min. 0 sec (no caching) max. 3600 sec (1h).

    OptsCacheLifeDAV = 60
        when the web resource is WebDAV.
        Min. 0 sec (no caching) max. 3600 sec (1h).

    OptsCacheLifeDAVLocked = 600
        when the web resource is WebDAV and it's locked by
	this LO instance (e.g. lock store has a lock to it).
        Min. 0 sec (no caching) max. 3600 sec (1h).

    OptsCacheLifeNotImpl = 3600
        when the web resource does not implement OPTIONS method.
        Min. 0 sec (no caching) max. 43200 sec (12h).

    OptsCacheLifeNotFound = 15
        when the requested web resource is not found on server.
        Min. 0 sec (no caching) max. 30 sec.

Change-Id: I719b97645e1d91a29134820b77678fd88fcb9ac2
Reviewed-on: https://gerrit.libreoffice.org/27684Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Giuseppe Castagno <giuseppe.castagno@acca-esse.eu>