CatalogUtilsTest: ported to Spock Framework.

Addressed to #151
CronServiceTest: ported to Spock Framework.

Addressed to #151
ImageServiceTest: ported to Spock Framework.

Addressed to #151
CountryServiceTest: ported to Spock Framework.

Addressed to #151
UserServiceTest: ported to Spock Framework.

Addressed to #151
SeriesServiceTest: removed unused member.

Should be in 588542290eebb6289f37e389141c08405ca73cf3 commit.

No functional changes.
SeriesServiceTest: ported to Spock Framework.

Addressed to #151
SiteServiceTest: ported to Spock Framework.

Addressed to #151
NEWS.txt: mention Spock Framework usage.

Addressed to #151
SeriesServiceTest: use Groovy's multiply operator instead of StringUtils.repeat().

No functional changes.
SeriesServiceTest: use Groovy collection's join() instead of StringUtils.join()

No functional changes.
CronServiceTest: use [] instead of Collections.emptyList().

No functional changes.
CatalogUtilsTest: use [] instead of Collections.emptySet().

No functional changes.
CatalogUtilsTest: use [] instead of Collections.singleton()

No functional changes.
CronServiceTest: use [] instead of Collections.singletonList()

No functional changes.
{Country,User}ServiceTest: use [] instead of new {Array,Linked}List()

No functional changes.
SeriesServiceTest: replaced self written method for constructing Set with [].

No functional changes.
CatalogUtilsTest: use [] instead of new LinkedHashSet().

No functional changes.
CronServiceTest: use Groovy's Date arithmetics instead of Calendar class.

No functional changes.