Fix 'echo "{{echo|foo&nbsp;bar}}" | tests/parse.js --wt2wt --editMode=yes'

The <span typeof="mw:Entity">&nbsp;</span> didn't have a TSR entry,
which was causing WSP.escapeTplArgWT to crash (note that the
documentation comment for escapeTplArgWT says that it assumes, "The
tokenizer sets tsr on all non-string tokens").

Add a zero-width TSR on the <span typeof="mw:Entity"> and </span> tags,
which makes WSP hum along happily.

Change-Id: I6c7ac05c918239de982f59e09b02110b8d755c11
Merge "Fix 'echo "{{echo|foo&nbsp;bar}}" | tests/parse.js --wt2wt --editMode=yes'"