Enhancement - related to, but not fixing bug #293

- Added new attribute modifiers 'word' and 'noword' which find the existence
  of whole words, or prove the non-existence of whole words.  If a task has
  the description "Pay the bill", then "description.word:the" will match, but
  "description.word:th" will not.  For partial word matches, there is still
  "description.contains:th".
- Added unit tests for the text.cpp functions.
- Added unit tests including the new modifiers in filters.
- Added unit tests to parse the new modifiers.
- Modified man page.
- Modified the Context::autoFilter processing to use the new modifiers for
  +tag and -tag filtering.
- Added a support email to an error message, while looking at the filter code.
- Added new modifiers to the help report.
- Modified a utf8.t unit test to include an alphanumeric tag, rather than a
  smiley face.

src/Filter.cpp

@@ -125,7 +125,7 @@ void Filter::applySequence (std::vector<Task>& all, Sequence& sequence)
     std::vector <int> right;
     listDiff (filteredSequence, (std::vector <int>&)sequence, left, right);
     if (left.size ())
-      throw std::string ("Sequence filtering error - please report this error");
+      throw std::string ("Sequence filtering error - please report this error to support@taskwarrior.org");
 
     if (right.size ())
     {