Currently paritions marked as encrypted by gen_esp32part.py are not
recognized as such and encrypted writes don't work.
This is part of espressif/esp-idf#253
The following issues mentioned during MR!341 review were fixed:
1) Core dump test application description
2) Usage of CONFIG_ESP32_ENABLE_COREDUMP_TO_FLASH and CONFIG_ESP32_ENABLE_COREDUMP_TO_UART
3) FLASH_GUARD_START macro usage is fixed in flash API
4) Core dump module logging facility
5) cache util functions doc updated
6) interactive delay before print core dump to uart
7) core dump partion support in build system
* App access functions are all flash encryption-aware
* Documentation for flash encryption
* Partition read/write is flash aware
* New encrypted write function
