Added broadcast for (extended) accessory commands

[reinder]

This PR adds broadcast commands <y a ...> for accessory and <y A ...> for extended accessory. Similar to the <l ...> command for engines/locomotives.

Without these broadcasts it is impossible to track these accessory command when multiple clients are involved.

Closes #444

[Asbelos]

This or introduces a pervasive change to the standard parsing algorithms which treat letters after the opcode as uppercase regardless of the case used. Thus the client side parsers can't distinguish between <y a and <y A.

It's important to consider the wider implications before implementing an apparently simple modification.

[Asbelos]

Didn't mean to close this...
But requires further consideration.

[reinder]

This or introduces a pervasive change to the standard parsing algorithms which treat letters after the opcode as uppercase regardless of the case used. Thus the client side parsers can't distinguish between <y a and <y A.

Sorry, I wasn't aware of that, we can change the A to a E for extended. I choose to use one opcode, because there aren't many opcodes left.

[Asbelos]

Please see my friend request on discord (ukbloke) where we can discuss more easily.

[reinder]

We've made contact on Discord.