Changes in BratWriter

[joancf]

refactoring of #1169

It adds some parameters to allow:

• indicate where the html template is located
• define the sorting order of the annotations above each span
• define the Feature to be shown for each annotation type

[ukp-svc-jenkins]

Can one of the admins verify this patch?

[reckart]

Jenkins, can you test this please?

[reckart]

@joancf Your changes rather target using the BratWriter to visualize annotations, not doing a lossless round trip CAS -> brat-format -> CAS, right? How about copying the BratWriter class into e.g. BratVisualizationWriter and focussing there on the kind of changes you made? That is probably easier for the moment than trying to handle the two use cases in the same component.