Mnemonic support

[oopsmonk]

Bump iota.c to d5a5f1e, added utf8proc external lib.

• replaced CONFIG_WALLET_SEED with CONFIG_WALLET_MNEMONIC
• Added CONFIG_ENG_MNEMONIC_ONLY, default is enabled, that only English mnemonic sentence is supported.
• implemented mnemonic_gen and mnemonic_update commands.
• Bump Wallet version to 0.4.0

Note:

For most IoT projects, the CONFIG_ENG_MNEMONIC_ONLY should be enabled for reducing the binary size.

• image size before adding mnemonic changes

Total sizes:
Used stat D/IRAM:   91656 bytes ( 236024 remain, 28.0% used)
      .data size:   12888 bytes
      .bss  size:   17328 bytes
      .text size:   61440 bytes
Used Flash size : 1846766 bytes
      .text     :  820776 bytes
      .rodata   :  173766 bytes
Total image size: 1921094 bytes (.bin may be padded larger)

• Image size with CONFIG_ENG_MNEMONIC_ONLY enabled

Total sizes:
Used stat D/IRAM:  108064 bytes ( 219616 remain, 33.0% used)
      .data size:   29272 bytes
      .bss  size:   17352 bytes
      .text size:   61440 bytes
Used Flash size : 2197906 bytes
      .text     :  833004 bytes
      .rodata   :  512678 bytes
Total image size: 2288618 bytes (.bin may be padded larger)

• Image size with CONFIG_ENG_MNEMONIC_ONLY disabled

Total sizes:
Used stat D/IRAM:  239136 bytes (  88544 remain, 73.0% used)
      .data size:  160344 bytes
      .bss  size:   17352 bytes
      .text size:   61440 bytes
Used Flash size : 2339258 bytes
      .text     :  833140 bytes
      .rodata   :  653894 bytes
Total image size: 2561042 bytes (.bin may be padded larger)