Fix offline mode and make it a bit more user friendly

Hopefully, there are not many new bugs :)
The notable changes in submodules are:

Submodule coffee-flask 9b74ccb..d99857c:
  > Center all content
  > Show current content of the offline queue when going offline
  > Do not allow multiple reconnect timers running simultaneously
  > When replaying offline queue, use the original event time rather than now()
  > Remove unused variable
  > Replace "fuck" with "ajax_failure"
  > Logout automatically even without selecting any beverage
  > Implement clean switching between online and offline mode
  > Catch all exceptions in JS function updateUI
  > Use new data structure for offline-collected data
  > Remove commented out code

Submodule terminal/src/mt-apps 89b7898..8a4c5fe:
  > Make it easier to call showOfflineQueue() from remote scripts
  > Replace tabs with spaces
  > Do not generate "empty" messages
  > Rework offline mode
  > Store offline data in an array rather than in a hash
  > Use more distinguishable user ids for simulated users
  > Replace tabs with spaces

diff --git a/coffee-flask b/coffee-flask
index 9b74ccb3aa3907ca51f5719fc4c9bf3121594fe4..d99857c0068d590bfea0a0bd00bc8bc1dd6fc4f1 160000 (submodule)
--- a/coffee-flask
+++ b/coffee-flask
@@ -1 +1 @@
-Subproject commit 9b74ccb3aa3907ca51f5719fc4c9bf3121594fe4
+Subproject commit d99857c0068d590bfea0a0bd00bc8bc1dd6fc4f1

diff --git a/terminal/src/buildroot b/terminal/src/buildroot
index 75cb61a4912d084dccc57836de4f1d4ebec8440a..82779ca806c7fc47aca470d0b339019179a0b07c 160000 (submodule)
--- a/terminal/src/buildroot
+++ b/terminal/src/buildroot
@@ -1 +1 @@
-Subproject commit 75cb61a4912d084dccc57836de4f1d4ebec8440a
+Subproject commit 82779ca806c7fc47aca470d0b339019179a0b07c

diff --git a/terminal/src/mt-apps b/terminal/src/mt-apps
index 89b7898554f1271d4bf38c562c6bfc46a7db03b2..8a4c5feb080e04607197d83084542c3d3cd5735c 160000 (submodule)
--- a/terminal/src/mt-apps
+++ b/terminal/src/mt-apps
@@ -1 +1 @@
-Subproject commit 89b7898554f1271d4bf38c562c6bfc46a7db03b2
+Subproject commit 8a4c5feb080e04607197d83084542c3d3cd5735c