T1, TI and CT -> title in Mendeley

The tags `T1`, `TI` and `CT` are mapped to `title` (in this order). If one exists all the other are ignored.

The following RIS file:

```none
TY - JOUR
T1 - T1 is 1st (I)
TI - TI is 2nd (I)
CT - CT is 3rd (I)
ER -

TY - JOUR
TI - TI is 2nd (II)
CT - CT is 3rd (II)
ER -

TY - JOUR
CT - CT is 3rd (III)
ER -

```

Should produce three references:

1. title="T1 is 1st (I)"
2. title="TI is 2nd (II)"
3. title="CT is 3rd (III)"

Reproduce the supplied RIS input through the parser and inspect how T1, TI, and CT are selected for the title. Done means the three records retain the first available tag in the stated order and produce the three expected titles.

Written by the indexing model from the issue text.