SDK default key and key switching

[henriqueaklein]

Implement the default frictionless initialization of the SDK (without any parameters).

• When initializing the SDK searches for a key/seed in the local secure storage.
• If found it boots from that.
• If not found it tries the IPC to see if someone on the same device has a key/seed/account for it, if it does, than it grabs that, store on local secure storage and boot.
• If none of the above, it creates a random key/seed with auto placeholder credentials and store it.

On a second moment, implement key switching where we connect to user informed credential, creating a transfer of funds from the placeholder to that