[devman] Capitalized filename is not mandatory anymore

doc/developer/tutorial.tex

doc/developer/tutorial/hello/src/Makefile.multiple-files

doc/developer/tutorial/hello/src/Makefile.single-file

doc/developer/tutorial/hello/src/hello.ml

doc/developer/tutorial/hello/v1-simple/hello.ml

doc/developer/tutorial/hello/v2-register/hello.ml

doc/developer/tutorial/hello/v3-log/hello.ml

doc/developer/tutorial/hello/v4-options/hello.ml

doc/developer/tutorial/hello/v5-multiple/hello.ml

doc/developer/tutorial/hello/v6-test-with-bug/hello.ml

doc/developer/tutorial/hello/v7-doc/hello.ml