[it] update 01-chapter9.markdown

Reviewed "I comandi interni di Git" paragraph.
Corrette alcune ortografie e la persona.
[it] update 01-chapter9.markdown

Reviewed "Impianto e sanitari".
Fixed many typos, reviewed the translation.
[it] 01-chapter9.markdown

Reviewed translation and fixed typos.
Completed "Gli oggetti di Git"
[it] 01-chapter9.markdown

Reviewed translation and fixed typos.
"Oggetti Albero"
test.txt was misspelled as text.txt, as well.