[#2116] remove cql code

doc/devel/Doxyfile

@@ -873,7 +873,6 @@ INPUT                  = ../../src/bin/agent \
                          ../../src/lib/cfgrpt \
                          ../../src/lib/config \
                          ../../src/lib/config_backend \
-                         ../../src/lib/cql \
                          ../../src/lib/cryptolink \
                          ../../src/lib/d2srv \
                          ../../src/lib/database \

doc/devel/cross-compile.dox

@@ -102,7 +102,6 @@ a native (i.e. not cross-compiled) Kea build.
 
 Required and optional Kea dependencies, usually available as packages:
  - Python (built-in)
- - Cassandra (skipped here)
  - libssl-dev (built-in in the full image)
  - liblog4cplus-dev (in liblog4cplus package, load both the library and
   the development part)

doc/devel/unit-tests.dox

@@ -389,29 +389,6 @@ local   all             postgres                                trust
   section in the <a href="https://kea.readthedocs.io">Kea Administrator
   Reference Manual</a>).
 
-
- @subsection cqlUnitTestsPrerequisites Cassandra database
-
- @todo: Describe steps necessary to set up Cassandra database suitable
- for running unittests.
-
- It seems this was enough:
-
- -# Launch cassandra if not running (-f for foreground)
- @verbatim
- % cassandra -f
- @endverbatim
-
- The tool is cqlsh:
-
- -# Run the tool
- @verbatim
- % cqlsh
- Connected to Test Cluster at 127.0.0.1:9042.
- [cqlsh 5.0.1 | Cassandra 3.11.1 | CQL spec 3.4.4 | Native protocol v4]
- Use HELP for help.
- cqlsh> @endverbatim\n
-
 @section unitTestsKerberos Kerberos Configuration for Unit Tests
 
 The GSS-TSIG hook library uses the GSS-API with Kerberos. While there are