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/text.h

@@ -52,6 +52,8 @@ void guess (const std::string&, std::vector<std::string>&, std::string&);
 bool digitsOnly (const std::string&);
 bool noSpaces (const std::string&);
 bool noVerticalSpace (const std::string&);
+bool isWordStart (const std::string&, std::string::size_type);
+bool isWordEnd (const std::string&, std::string::size_type);
 
 #endif
 ////////////////////////////////////////////////////////////////////////////////