Store certificate in PEM, fixed keys PEM type

See merge request !5

Resolve "Make private key to be persisted just in PEM format"

Closes #4

See merge request !4

Fixed key type for aes key persistence

See merge request !3

Resolve "Add new key type - AES key"

Closes #3

See merge request !2

Removed AES and nonce parameters from operations, fixed generate certificate to use Vereign CA private key

40-key-storage-service-api

Closes #1

See merge request !1

Added encryption for generated key pair and certificate, made generated certificate to be signed with Vereign CA certificate, added validation for UUID already in use, added revoked field and operation