CommonRegexes.Date: accept incomplete dates

[IhateTrains]

CK3 has multiple instances of incomplete dates in character history. Some log lines from IRToCK3:

2024-05-01 15:03:12 [DEBUG] Ignored history keywords: 640.1.
2024-05-01 15:03:12 [DEBUG] Ignored history keywords: 889
2024-05-01 15:03:12 [DEBUG] Ignored history keywords: 1019.1.
2024-05-01 15:03:12 [DEBUG] Ignored history keywords: 1058.1.
2024-05-01 15:03:12 [DEBUG] Ignored history keywords: 1065.1.
2024-05-01 15:03:13 [DEBUG] Ignored history keywords: 1077.1
2024-05-01 15:03:13 [DEBUG] Ignored history keywords: 1101.1
2024-05-01 15:03:14 [DEBUG] Ignored history keywords: 976.1
2024-05-01 15:03:14 [DEBUG] Ignored history keywords: 880.1.1.
2024-05-01 15:03:14 [DEBUG] Ignored history keywords: 1049
2024-05-01 15:03:15 [DEBUG] Ignored history keywords: 939.1.
2024-05-01 15:03:15 [DEBUG] Ignored history keywords: 841.1.1.
2024-05-01 15:03:15 [DEBUG] Ignored history keywords: 1046
2024-05-01 15:03:15 [DEBUG] Ignored history keywords: 879.1.

[coveralls]

Pull Request Test Coverage Report for Build 8912899100

Details

• 16 of 16 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.07%) to 92.996%

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Totals
Change from base Build 8877018128:	0.07%
Covered Lines:	3390
Relevant Lines:	3609

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💛 - Coveralls

[IhateTrains]

Reworked the Date constructor to accept incomplete dates. Ready for review again.