Fix parsing of years ending in zero

Assume year precision instead of automagically converting
and assuming precision of decade, millenium, etc.

Require explicit precision option for setting those precisions.

In Wikibase, precision can be set via advanced options in the
time widget, via the api (e.g. bot edit), or providing certain
specific text input (e.g. '19. century').

Note: We should be flexible in the future on what to parse,
such as '19th century'. (see bug 64545)

Bug: 64537
Update test cases to use year precision, unless otherwise specified
Default to year precision date in range 4000 BC to 4000
Fix TimeParserTest namespace
Update release notes
Merge pull request #16 from DataValues/precision

Fix parsing of years ending in zero