Improve messages workflow

[misstick]

Improve features

• [x] upgrade unread messages counter into menu as fast as possible,
• [x] active realtime events,
• [x] fix nextURL setting,
• [x] do not fetch all messages to get conversationLength,
• [x] fetch all messages from conversation when a message is displayed,
• [x] show only current message on 2nd panel,
• [x] reset currentID when Route changes,
• [x] clean messageList dead code,
• [x] fix keyboard navigation for top and bottom keys,
• [x] fix filter navigation,
• [x] fix checkbox selection,

- [ ] selection menu: remove tools submenu to display simple buttons

Remove features

• [x] search bar is useless (search is broken),
• [x] filter toolbar,
• [x] add mailbox unread,
• [x] add mailbox important,
• [x] compose was re-added but should disappear, see: https://github.com/cozy/cozy-emails/pull/807

[frankrousseau]

I didn't notice before but it looks like you don't follow the 80 chars guideline. Could you stick to it? It makes the text size standard, force to write more concise code and match with what we do since the beginning.

[m4dz]

I merge as it, maybe we need to think about:

• using Getter in component and never call Stores directly
• Use dedicated getters for stores like MessagesStores, and not let RouterGetter serves contents that doesn't rely directly on it (like getMessagesList, which should be in a MessagesGetter that can ask RouterSTore for the current mailboxID)

We also need to add a lot of comments in the whole app: each time I review, it's deeply hard to understand who does what, how, and what have changed :disappointed:…

[misstick]

@m4dz :

• " using Getter in component and never call Stores directly" : this should be done a little each time
• for getter, we could talk about this; to my mind, having only one getter si enought but its name should be change in getters/application ie.