Import account

Closes #20 (closed).

• Made the create account step indicator work
• Factorized the account header into a <CreateAccountHeader> component
• Added a import account feature. It works like this:
  1. On step 1, user can check the Import Account feature, and choose a name for this account
  2. Then he'll be redirected to input his phrase (that he previously wrote on a paper)
  3. Then choose password, then confirm

1 & 2's order can be changed, i.e. 1st input phrase, then choose account name.