fix library loading order (issue #111)

This version introduces multiple enhancements:

fixed load in interfaces and abstract classes before normal class
split mysql library to two classes
changed name of sql abstract class

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

Added:      /BLUE_FRAMEWORK/packages/db/mysql_connection_class.php
            -- Added --
                mysql_connection_class in separated file

Modified:   /index.php
            -- Added --
                $_loadedLibraries variable to keep list of loaded libraries
                _loadLibraryFiles to load all given libraries
                _skipLibrary to check that library must be loaded
                _readDirectory to get all interfaces, abstract and class from directory
            -- Updated --
                package, added handling of new methods responsible for reading package and loading libraries

Modified:   /BLUE_FRAMEWORK/modules/mod2/mod2.php
            -- Updated --
                changed names of required libraries

Modified:   /BLUE_FRAMEWORK/cfg/tree.xml
            -- Updated --
                names of libraries to load

Modified:   /BLUE_FRAMEWORK/packages/db/mysql_class.php
            -- Updated --
                changed extended class name
            -- Removed --
                mysql_connection_class and moved to separated file
Modified:   /BLUE_FRAMEWORK/packages/db/mssql_class.php
            -- Updated --
                changed extended class name

Modified:   /BLUE_FRAMEWORK/packages/db/fb_class.php
            -- Updated --
                changed extended class name

Modified:   /BLUE_FRAMEWORK/packages/db/xmlDB_class.php
            -- Updated --
                changed extended class name

Modified:   /BLUE_FRAMEWORK/packages/db/sql_abstract.php
            -- Updated --
                changed class name