Make full example modules (issue #20)

This version introduces multiple enhancements:

Finished example with communication between modules and usage of module configuration

Details of additions/deletions below:
--------------------------------------------------------------

Added:      /BLUE_FRAMEWORK/modules/example_modules/elements/dtd/config.dtd
            -- Added --
                module configuration DTD

Added:      /BLUE_FRAMEWORK/modules/example_modules/elements/config.xml
            -- Added --
                module configuration file

Added:      /BLUE_FRAMEWORK/modules/example_modules/example_modules.php
            -- Added --
                example module main file

Added:      /BLUE_FRAMEWORK/modules/example_modules/lang/example_modules_en-GB.php
            -- Added --
                english translations

Added:      /BLUE_FRAMEWORK/modules/example_modules/lang/example_modules_pl-PL.php
            -- Added --
                polish translations

Added:      /BLUE_FRAMEWORK/modules/example_modules_reader/example_modules_reader.php
            -- Added --
                example module reader main file

Added:      /BLUE_FRAMEWORK/modules/example_modules_reader/lang/example_modules_reader_en-GB.php
            -- Added --
                english translations

Added:      /BLUE_FRAMEWORK/modules/example_modules_reader/lang/example_modules_reader_pl-PL.php
            -- Added --
                polish translations

Added:      /BLUE_FRAMEWORK/modules/example_modules/layouts/index.html
            -- Added --
                example module template

Added:      /BLUE_FRAMEWORK/modules/example_modules_reader/layouts/index.html
            -- Added --
                example module reader template

Modified:   /BLUE_FRAMEWORK/cfg/lang/core_en-GB.php
            -- Added --
                english example description

Modified:   /BLUE_FRAMEWORK/cfg/lang/core_pl-PL.php
            -- Added --
                polish example description

Modified:   /BLUE_FRAMEWORK/elements/layouts/examples/examples.html
            -- Added --
                description marker

Modified:   /BLUE_FRAMEWORK/cfg/tree.xml
            -- Added --
                example_modules page and two example modules