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/report.cpp

@@ -260,6 +260,8 @@ int longUsage (std::string &outs)
       << "  hasnt"                                                            << "\n"
       << "  startswith (synonym left)"                                        << "\n"
       << "  endswith   (synonym right)"                                       << "\n"
+      << "  word"                                                             << "\n"
+      << "  noword"                                                           << "\n"
       <<                                                                         "\n"
       << "  For example:"                                                     << "\n"
       << "    task list due.before:eom priority.not:L"                        << "\n"