QPID-4558: Selectors for C++ broker
- Add support for link property qpid.selector to client messaging library
  queue addresses.
QPID-4558: Selectors for C++ broker
- Added simple selector framework to broker.
- Added in infrastructure for selector evaluation
-- Put in place a trivial (but real) selector:
   The expression specifies a message property
   and returns true if it is present.
QPID-4558: Selectors for C++ broker-
- Added some parser documentation
QPID-4558: Selectors for C++ broker
- Added in beginnings of parser
QPID-4558: Selectors for C++ broker
- Added start of some evaluation logic
QPID-4558: Selectors for C++ broker
Start of some parsing logic
Finished initial set of tokenisers (numerics are left)
Split out selector tokeniser
Added unit test framework
- Fixed completely erroneous less than comparison
- Fixed wrong tokeniseIdentifierOrReserved word logic
(yay for unit tests!)
- Added unit tests
QPID-4558: Selectors for C++ broker
Finished initial tokenisers and unit tests for them
- Finished simplest parser
[but no unit tests so not working yet]
QPID-4558: Selectors for C++ broker
Finished simple expression parser and unit tests
- will parse and execute the forms:
*  A=B
*  A<>B
*  I IS NULL
*  I IS NOT NULL
- where A, B are strings or identifiers
-       I is an identifier
Split Selector expression parsing and evaluation into its own files
Changed the interface to the tokeniser to avoid tokenising the same
characters more than once.
Fix memory issues
- Changed interface to tokeniser to return const ref to toke already held
  in the tokeniser token stream.
- Tested and fixed return token to Tokeniser.
- Fleshed out conditional expressions a bit more (AND,OR, parentheses)
- Added debug output for parse
- Added unary NOT to the operations and tests
Added some comment documentation about special identifiers
Added missing reserved word ("escape")
Initial work on special identifiers
- Simple if chain to get values (more to fill in)
- needed to allow "." as a valid character in identifiers
  (it's not valid in JMS selectors)