Date model improvements

[lfoppiano]

Some improvements to be added to the grobid-core date model:

• [x] (design/minor) move the date labels in TaggingLabels.java ~~- [ ] Add optional time information in the parsing phase (e.g. <hour>:<minutes>:<seconds>.<milliseconds> TZD) https://www.w3.org/TR/NOTE-datetime~~
• [x] Check whether the normalisation phase could be replaced using https://github.com/HeidelTime/heideltime/issues

[lfoppiano]

Here a collection of sample that could be improved:

19 January 19 83 is not correctly normalised, though it's correctly extracted:

CRF output:

19	19	1	19	19	19	9	19	19	19	LINESTART	NOCAPS	ALLDIGIT	0	0	0	NOPUNCT	<date>	I-<day>
.	.	.	.	.	.	.	.	.	.	LINEIN	ALLCAP	NODIGIT	1	0	0	DOT	<date>	I-<other>
January	january	J	Ja	Jan	Janu	y	ry	ary	uary	LINEIN	INITCAP	NODIGIT	0	0	1	NOPUNCT	<date>	I-<month>
19	19	1	19	19	19	9	19	19	19	LINEIN	NOCAPS	ALLDIGIT	0	0	0	NOPUNCT	<date>	I-<year>
83	83	8	83	83	83	3	83	83	83	LINEEND	NOCAPS	ALLDIGIT	0	0	0	NOPUNCT	<date>	<year>