pw_kvs: Initial commit of new KVS design

Builds, but lots more work needed.

Fun fact: this code was written collaboratively in a Google Doc.

Change-Id: I8a89c5d0fdc71ec28cf432350e65d17e24a6f25c
diff --git a/pw_kvs/BUILD b/pw_kvs/BUILD
index 53d5579..5433285 100644
--- a/pw_kvs/BUILD
+++ b/pw_kvs/BUILD
@@ -25,16 +25,17 @@
 pw_cc_library(
     name = "pw_kvs",
     srcs = [
-        "flash.cc",
+        "checksum.cc",
+        "flash_memory.cc",
         "key_value_store.cc",
+        "pw_kvs_private/format.h",
+        "pw_kvs_private/macros.h",
     ],
     hdrs = [
-        "public/pw_kvs/assert.h",
-        "public/pw_kvs/flash.h",
+        "public/pw_kvs/checksum.h",
         "public/pw_kvs/flash_memory.h",
         "public/pw_kvs/in_memory_fake_flash.h",
         "public/pw_kvs/key_value_store.h",
-        "public/pw_kvs/partition_table_entry.h",
     ],
     includes = ["public"],
     deps = [