Break the modules invenio_tools and harvest_tools

• The modules invenio_tools is too big. It contains 4 classes, 5 exceptions and its length is about 2680 lines
• The modules harvest_tools is also too long. It contains 10 classes, 6 functions and its length is about 1970 lines
• Transform these modules in packages with the same name. The packages contains several sub-modules, one per class. Add one base sub-module for regular expression, functions used in several places,...
• In addition the translation (gluon.current.T) of the error message is performed at the initialisation of the modules invenio_tools. Remove the translation, it can be done later on, in the error handler.