improved `isAvailable`, checkes all record structs, inverter becomes available more early because version is check first
fix tickers were not set if NTP is not available
disabled annoying `FlashStringHelper` it gives randomly Expeptions during development, feels more stable since then
moved erase button to the bottom in settings, not nice but more functional
split `tx_count` to `tx_cnt` and `retransmits` in `system.html`
fix mqtt retransmit IP address #602
added debug infos for `scheduler` (web -> `/debug` as trigger prints list of tickers to serial console)