Migrate mqbblp docs directory into a Doxygen file

This patch removes the old `doc/*.txt` file and migrates some
information in it into a file Doxygen can read.  The information not
migrated is:

  1. the table of contents for this package, which is very out-of-date and will
  be generated by Doxygen automatically, and kept in-sync with any
  documentation changes made in the files, and

  2. the hierarchical synopsis, which is also out-of-date.

This continues the changes made in commit cb037c6.

Signed-off-by: Patrick M. Niedzielski <[email protected]>

Author: pniedzielski

src/groups/mqb/mqbblp/README.dox

@@ -0,0 +1,8 @@
+/**
+@dir mqbblp
+
+@brief The `MQBBLP` (Message Queue Broker Bloomberg LP) package provides
+Bloomberg implementation of queue management.
+
+This package provides implementation of queues.
+*/