MDL-41882 tool_generator: Refactoring backend class

Moving it to course_backend keeping generic
methods and attributes in backend class.

AMOS BEGIN
 MOV [size_0,tool_generator],[coursesize_0,tool_generator]
 MOV [size_1,tool_generator],[coursesize_1,tool_generator]
 MOV [size_2,tool_generator],[coursesize_2,tool_generator]
 MOV [size_3,tool_generator],[coursesize_3,tool_generator]
 MOV [size_4,tool_generator],[coursesize_4,tool_generator]
 MOV [size_5,tool_generator],[coursesize_5,tool_generator]
AMOS END
MDL-41882 tool_generator: Adding maketestsite script

Uses maketestcourse.php to set up
a test site.
MDL-41882 tool_generator: New unit test