[WIP] Reuse existing instrument when recreating a new instrument with same name and type

[jenshnielsen]

This should remove one of the most common errors for users working interactively with qcodes

Obviously still a few issues:

• See inline comment about checking that this is the same physical instrument.
• Type checking could be cleaner
• New tests and adaptions of old tests
• Add bolean for recreate true - false

Now that this implements everything that find_or_create_instrument does
we can also remove the use of than + perhaps deprecate it.