Implement Serial Console app & more (#239)

- Implemented new app: Serial Console
- `Uart::writeString()`: fixed 2 mutex bugs
- `AlertDialog::start()` with default "OK" button added
- Created `tt::lvgl::defaultLockTime` for re-use
- Removed various usages of deprecated `lvgl::obj_set_style_no_padding()`
- Implemented `hal::uart::getNames()` to list all interface names

Documentation/ideas.md

@@ -33,6 +33,9 @@
 - Scanning SD card for external apps and auto-register them (in a temporary register?)
 - Support hot-plugging SD card
 - All drivers (e.g. display, touch, etc.) should call stop() in their destructor, or at least assert that they should not be running.
+- Use GPS time to set/update the current time
+- Investigate EEZ Studio
+- Remove flex_flow from app_container in Gui.cpp
 
 # Nice-to-haves
 - Give external app a different icon. Allow an external app update their id, icon, type and name once they are running(and persist that info?). Loader will need to be able to find app by (external) location.
@@ -66,3 +69,7 @@
 - GPS app
 - Investigate CSI https://stevenmhernandez.github.io/ESP32-CSI-Tool/
 - Compile unix tools to ELF apps?
+- Calculator
+- Text editor
+- Todo list
+- Calendar