ZMS is the abreviation of Zephyr Memory Storage.
It is a storage developed to target especially the non erasable devices.

The new memory storage system inherit from the NVS storage multiple
features and introduce new ones :
* Inherited features :
 - light key-value based storage
 - cache for entries
 - Wear Leveling of flash memory
 - Resilience to power failures
* New features :
 - cycle counter for non erasable devices (instead of erase emulation)
 - Keys up to 32-bit
 - Built-in support of CRC32 for data
 - Small size data (<= 8 bytes) integrated within entries

Signed-off-by: Riadh Ghaddab <rghaddab@baylibre.com>

List of added tests :
- zms.test_delete
- zms.test_zms_cache_collission
- zms.test_zms_cache_gc
- zms.test_zms_cache_hash_quality
- zms.test_zms_cache_init
- zms.test_zms_corrupted_sector_close_operation
- zms.test_zms_corrupted_write
- zms.test_zms_full_sector
- zms.test_zms_gc
- zms.test_zms_gc_3sectors
- zms.test_zms_gc_corrupt_ate
- zms.test_zms_gc_corrupt_close_ate
- zms.test_zms_mount
- zms.test_zms_write

Signed-off-by: Riadh Ghaddab <rghaddab@baylibre.com>

This adds a user application that shows the usage of ZMS
The sample app shows three main functions of ZMS:
- read/write/delete key/value pairs
- fill all storage and delete it
- calculate free remaining space

Signed-off-by: Riadh Ghaddab <rghaddab@baylibre.com>

This adds the documentation for the Zephyr Memory Storage system.

Signed-off-by: Riadh Ghaddab <rghaddab@baylibre.com>