Added Italian mnemonics set

[paoloaga]

Here you can find the proposed Italian wordlist for BIP0039.

Words have been chosen using the following rules:

1. Simple and common italian words.
2. Length between 4 and 8 characters.
3. First 4 letters must be unique between all words.
4. No accents or special characters.
5. No complex verb forms.
6. No plural words.
7. No words that remind negative/sad/bad things.
8. If both female/male words are available, choose male version.
9. No words with double vocals (like: lineetta)
10. No words already used in other language mnemonic sets.
11. If 3 of the first 4 letters are already used in the same sequence in another mnemonic word, there must be at least other 3 different letters.
12. If 3 of the first 4 letters are already used in the same sequence in another mnemonic word, there not must be the same sequence of 3 or more letters.

Rules 11 and 12 prevent the selection words that are not different enough. This makes each word more recognizable among others and less error prone. For example: the wordlist contains "atono", then "atomo" is rejected, but "atomico" is good.

All the words have been manually selected and automatically checked against the rules.

Words have been checked automatically against an italian dictionary and spell-checker and reviewed one by one.

[paoloaga]

I accidentally closed the pull request while doing a rebase on the branch. Pull request #306 is final.