Cleanup submodules

Exchanged submodules with forked repositories:

• arduino-esp32
• NeoPixelBus

Changed to esp-idf head v3.3-beta1-504-g6c49f1924

Added beep volue control, idle handling

Merge pull request #37 from an-erd/featurebranch

- Beep volume control added
- Idle timer functions added

Display optimized, Archiver added (SD card), OTA implementation

Basic disPOD features from Rel. 0.1:

• Connect WiFi to known APs
• BLE scanning, connecting, notification for MilestonePod
• show real time running values for cadence, strike, GCT (ground contact time)

Additional features in Rel. 0.2:

• Archiver w/timestamps (file and log data) to SD card
• Display flickering resolved (sprite implementation)
• display text sizes adjusted (inc. in running screen, optimized in status screen)
• queue monitoring in running screen (running values/time stamps) with on/off functionality
• BLE disconnect handling
• status for WiFI and BLE standardized
• updated TFT_eSPI to commit 33d9313 (forked repository an-erd/M5Stack)
• OTA implementation (WIP due to unresolved Guru Meditation Error in context of BT and cache memory region access)

Bug fixes, in particular

• SPI coexistence of display, SPIRAM, SD card
• Fixes of workflow, fault tolerance, retry features