Hide server label in room panel when input is hidden

Small german locale improvements

* Rename onConnStatusChanged to onConnectStatusChanged
* Provide human readable debug feedback on onConnectStatusChanged

Split the code into two new methods for the prebind and non-prebind
usecase.

More small improvements to german locale

Also fixed a CSS bug. Chat box's width wasn't responsive.

mentioning plugins architecture refactoring.

Improve de locale

- TrimChats was called before a newly maximized chat had its final width which
  prevented it from working as intended.
- We cannot check for available space by using the width of the #conversejs
  element anymore, since it now has variable (auto) width. So we check against
  the body width instead.

Merge branch 'icomoon-xa-icon' of https://github.com/thierrytiti/converse.js into thierrytiti-icomoon-xa-icon

Merge branch 'MUC-toggle-Call' of https://github.com/thierrytiti/converse.js into thierrytiti-MUC-toggle-Call

fonts built with icomoon

https://github.com/jcbrand/converse.js/commit/47e00ae005fc4034836595d4267953b46a869cb7

- HAS_CSI might be called before features have been received. Instead, set a
  flag whenever a feature is received and check for that flag.
- Converse.ping was sending stanzas to the bare jid instead of to the domain.
- The handler that updates the date the last stanza was received must return
  true so that it gets called again.
- Only register the Pong handler if Ping is enabled.
- Rename lastMessage to lastStanzaDate to make it more clear.

Also use and add a Strophe namespace for CSI.