Update submodules

* coffee-flask e21678b...9a9446d (28):
  > Add comments
  > Workaround the incompatibility created by Matplotlib 3.3.0
  > Suppress Matplotlib's deprecation warning
  > Add TODO
  > Add doc string
  > Add `type` for flavors and build current consumption dynamically
  > Add new beverage `tea` and make buttons larger
  > Add missing quotes in JS handler for disabling identifier
  > Include constant SQL values directly in queries
  > Update debug message
  > Rename DB field identifiers.status to identifiers.active
  > Add support for multiple identifiers per user
  > Wrap long line and unify upper-casing of SQL keywords
  > Separate counting of coffees and club-mate
  > Remove last coffe pack opened button
  > Add support for another beverages (namely club mate)
  > Change the name of the configuration file
  > Fix column name in UNIQUE index
  > Fix duplicate recording of coffees
  > English fixes
  > Make config-related error message more informative
  > Add last coffee pack button
  > Fix data acquisition for flavor graph.
  > Add TODO
  > Add graphs with total coffee consumption on login screen
  > Fix tag in 'user' template
  > Remove unused function
  > Fix incorrect counting of coffees made during time close to midnight

* terminal/src/buildroot 82779ca806...f98ee51dee (2):
  > overlay: Enable useful munin plugins
  > munin-c: Add iostat plugin and fix memory plugin

* terminal/src/mt-apps 8a4c5fe...b50bf70 (2):
  > mt_server: Use "%s" format string in syslog()
  > Uses letters in test identifiers, not only numbers

diff --git a/coffee-flask b/coffee-flask
index e21678bdd78e26ef9586ebbd641cb39239d74d8f..9a9446d8a21e19e4acfed23d123afcdccc13604c 160000 (submodule)
--- a/coffee-flask
+++ b/coffee-flask
@@ -1 +1 @@
-Subproject commit e21678bdd78e26ef9586ebbd641cb39239d74d8f
+Subproject commit 9a9446d8a21e19e4acfed23d123afcdccc13604c

diff --git a/terminal/src/buildroot b/terminal/src/buildroot
index 82779ca806c7fc47aca470d0b339019179a0b07c..f98ee51dee15725855874ffd0fa86ba2f9505125 160000 (submodule)
--- a/terminal/src/buildroot
+++ b/terminal/src/buildroot
@@ -1 +1 @@
-Subproject commit 82779ca806c7fc47aca470d0b339019179a0b07c
+Subproject commit f98ee51dee15725855874ffd0fa86ba2f9505125

diff --git a/terminal/src/mt-apps b/terminal/src/mt-apps
index 8a4c5feb080e04607197d83084542c3d3cd5735c..b50bf70821570b0dd9ed2af1ee54e580296efe4f 160000 (submodule)
--- a/terminal/src/mt-apps
+++ b/terminal/src/mt-apps
@@ -1 +1 @@
-Subproject commit 8a4c5feb080e04607197d83084542c3d3cd5735c
+Subproject commit b50bf70821570b0dd9ed2af1ee54e580296efe4f