Case (in)sensitivity of addresses

### Step 1: Please describe your environment

* ZeroNet version: master
* Platform: various linux distros

### Step 2: Describe the problem:

Trying to load address which coincides with a registered one up to letter case leads to weird behaviour. In particular, the page loads forever, only changing its title to one from original page (if it's loaded)

#### Steps to reproduce:

1. take any site address
2. load/try to load the address
3. change case of one (or many) of its alphabetic components
4. try to load that one

#### Observed Results:

There is no attempt to load the second address, the page is empty and "loads" forever

E.g. http://127.0.0.1:43110/1HeLLo4uzjaLetFx6NH3PMwFP3qbRbTf3d

#### Expected Results:

Sites with different addresses should be independent of each other

既知のサイトアドレスと、大文字・小文字を変更したバリエーションを使って、提供された再現手順を実行し、その後の読み込み動作を比較します。大文字・小文字だけが異なるアドレスが独立したサイトとして扱われ、2つ目のページが空白のままになったり、読み込みが永遠に続いたりしなければ完了です。

索引モデルが issue の本文から書いたものです。