Make "connect" button blue and change the copy a bit

[Tbaut]

closes #389

There's 1 case when we have 2 buttons primary on a page, but it's doing the same thing, so I guess it's ok.

• Connect and Connect wallet buttons are now blue
• Change the copy "Watch One" -> "Wach address" since the "one" we're referring to makes no sense, one what, wallet?
• "Connect extension" to "Connect wallet" to be future proof if we want to use WalletConnect or anything else

I used this opportunity to refactor the Home that was having a lot of duplicate code. This means please check that the correct messages are displayed when they should (BTW let's make a test for this, edit: #412)

• Multix welcome message when brand new landing
• No account found when clicking on connect without an extension
• No multisig found when an account is shared in the extension but there's no msig and watched address is empty

Submission checklist:

Layout

• Change inspected in the desktop web ui
• Change inspected in the mobile web ui

Compatibility

• Functionality of change validated with a connected account with multisig
• Applicable elements hidden / disabled for watched multisigs / pure

[Lykhoyda]

Looks good 👍

[asnaith]

Left one little suggestion for consistency but other than that looks great.

The appropriate message is displayed for all of the scenarios listed.