synchronized up to the mcu-tool/mcuboot 4eca54f4

Synchronized to:
https://github.com/mcu-tools/mcuboot/commit/4eca54f4175c76c4525ac0f1eb867ffb7d40e165



- added precise check of the image size
- loader: Added post copy hook to swap function
- added Kconfig option for setting swap using move as default swap algorithm
- zephyr: fixed ram loading for ARM, with correct handling of vector table when code has moved to RAM.

- imgtool: add option to export public PEM

merged using GitHub web gui.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>