Add Implicit Account Validation Rules

[PhilippGackstatter]

Description of change

Add implicit account creation and conversion validation rules in the VM.

Implements part of iotaledger/iota-core#278.

Type of change

• Enhancement (a non-breaking change which adds functionality)

How the change has been tested

Added tests.

Change checklist

Add an x to the boxes that are relevant to your changes, and delete any items that are not.

• My code follows the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests using ginkgo that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes