add ability to skip sections of source file

[miki725]

In some scenarios, before an import is made, it requires another import which also needs to execute a regular Python statement:

import a
a.foo()
import b # requires both statements above

There should be ability to skip such import sections:

<imports>

# block importanize                         |    
import a                                    | will
a.foo()                                     | not be
import b # requires both statements above   | organized
# endblock importanize                      |

<more imports>