encrypted-messages

Currently we use the word "Option" which is inconsistent and may cause confusion.

Example:

# Option: "alloc" enables support for heap allocation on "no_std"
# platforms, requires nightly.
alloc = ["ockam_core/alloc", ...

Should rather be:

# Feature: "alloc" enables support for heap allocation on "no_std"
# platforms, requires nightly.
alloc = ["ockam_core/all

for example:

• limit number of kdf iterations for out of order message delivery
• limit max message size
• patch serde_cbor to limit maximum memory allocation

I'm not sure how best to pick these limits, so for now I'm going to leave TODO's in the code that reference this issue.

(probably partial) list of places in the code where this needs to be fixed:

• read_cbor
• `send_

Is your feature request related to a problem? Please describe.
The modal needs to display buttons related to mailchain/mailchain-web#157

Describe the solution you'd like
Buttons to include (no need to add methods):

• Back: takes user back to Step 1
• Cancel: close model and discards changes
• Save Changes: Save changes and load the sel