Feature: extend I&M API so that a user is able to use I&M5 and modify its content as well

Customers who sell their product with Hilscher Profinet IO Device loadable firmware inside to companies that brandlabel the product need a way to modify I&M5 data.

The following requirements need to be fullfilled:

• customer needs API to modify I&M5 data answered by protocol stack
• customer needs API to enable application I&M5 handling
• existing Read I&M API needs to be extended to offer API for customer to handle I&M5

In addition the following enhancements to protocol stack API is requested

• customer needs API to read out the I&M5 data the protocol stack would answer to the network
• customer needs API to read out the I&M0 data the protocol stack would answer to the network

By default if customer wants to handle I&M data only I&M0..4 is forwarded by protocol stack to application. I&M5 is answered with "invalid index". Only if customer explicitly enables I&M5 handling the new API is used by protocol stack and the request is forwarded to application.
Write Requests to I&M5 are always rejected by the protocol stack directly.

The API shall be equal to the one implemented in PNSv3.