TigerXmlReader produces wrong begin and end index for target (SemPred) of a semantic frame when the target is noncontiguous.

For instance in the following sentence:
w1 w2 w3 w4 w5 w6 w7

, if a target consists of w2 and w5 then the corresponding begin and end indexes for target will be wrongly set as:

target.begin = w2.begin;
target.end = w5.end;

To fix this issue:

• modify the reader so that in this case it returns the offset for first token (w2 in this case)
• merge boundary of neighboring tokens inside a frame
• produce appropriate warning message when a frame spans over noncontiguous tokens
• implement a data structure (e.g. List) to store all constituents of a target