Support Equiv relations in brat format

[reckart]

Is your feature request related to a problem? Please describe. The import of brat data fails if the file contains an Equiv relation.

Schema:

[relations]
Equiv	Arg1:Protein, Arg2:Protein, <REL-TYPE>:symmetric-transitive

Format:

*	Equiv T1 T13

Describe the solution you'd like Support Equiv relations in brat format.