ndn-tool unit tests

Assumptions

Unit tests for a tool foo should be placed in the folder foo and build script for the tool should define foo-objects that includes all object files for the tool, except object files defining main function.

For example,

bld(features='cxx',
    name='tool-subtool-objects',
    source=bld.path.ant_glob('subtool/*.cpp', excl='subtool/main.cpp'),
    use='core-objects')

bld(features='cxx cxxprogram',
    target='../../bin/subtool',
    source='subtool/main.cpp',
    use='tool-subtool-objects')

bld(name='tool-objects',
    use='tool-subtool-objects')