Version independent external apps (standalone apps) (#2145)

This pull requests adds a new type of external app to the firmware: The standalone app.

Pros:

Will work after an upgrade.
Size of image is only limited by shared heap size of M0 (application) (64kb total).
Cons:

No full access to all functions in the main firmware. One well defined (and versioned) API handles all communication.
The Pacman app was converted to be the first the the new kind.

firmware/CMakeLists.txt

@@ -50,6 +50,7 @@ endif()
 
 add_subdirectory(application)
 add_subdirectory(baseband)
+add_subdirectory(standalone)
 add_subdirectory(test)
 
 # NOTE: Dependencies break if the .bin files aren't included in DEPENDS. WTF, CMake?
@@ -88,7 +89,7 @@ add_custom_target(
 	program-external-apps
 	WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
 	COMMAND ${PROJECT_SOURCE_DIR}/tools/copy_external_apps.sh
-	DEPENDS program
+	DEPENDS program standalone_apps
 )
 
 add_custom_command(
@@ -100,8 +101,9 @@ add_custom_command(
 	COMMAND cp ${FIRMWARE_FILENAME} firmware_tar/FIRMWARE/portapack-mayhem_${VERSION_NOHASH}.bin
 	COMMAND mkdir -p firmware_tar/APPS
 	COMMAND cp application/*.ppma firmware_tar/APPS
+	COMMAND cp standalone/*/*.ppmp firmware_tar/APPS
 	COMMAND cd firmware_tar && tar -cvaf ../${PPFW_FILENAME} *
-	DEPENDS firmware ${FIRMWARE_FILENAME}
+	DEPENDS firmware ${FIRMWARE_FILENAME} standalone_apps
 	# Dont use VERBATIM here as it prevents usage of globbing (*)
 	# There shouldnt be any funny business in the filenames above :)
 )