Add breakpoints to the REPL

[Flu]

Goal

The current REPL, among its many problems, is that it doesn't feature any breakpoint functionality. The point of this task is to add breakpoints to it, making debugging even easier than before.

Requirements

The following commands should be supported:

1. set a breakpoint, like break <address>, where address is the hexadecimal/decimal address of the instruction on which the breakpoint will activate. The command should fail if the address is invalid or if there's already a breakpoint at that location.
2. show all breakpoints, like show break. This should return a list of breakpoints, each with their own id, their address and the instruction at that address.
3. delete a breakpoint based on its id: delete break <id> or d break <id>

[Flu]

Couple more points:

• Since this issue will require you to pass more information to the run- functions (runUntilProgramEnd, runUntilFunctionEnd, etc.), encapsulate the program memory and the future breakpoint list in a record and pass that instead. It will make things easier.
• Since now breakpoints will be a thing, it would be very useful to see which lines have a breakpoint on them when you print the instructions in the REPL with the i command. Currently, the output looks like this:

avr-emulator> i
0x0007     SUB 18 19
0x0008     AND 16 18
0x0009     ADIW 27 26 5
0x000A     SUBI 16 15
0x000B     ANDI 17 240
0x000C     CP 16 17
0x000D     BREQR 1

But it would be nice to show something akin to this, if, for example, there's a breakpoint on address 0x000C:

avr-emulator> i
0x0007          SUB 18 19
0x0008          AND 16 18
0x0009          ADIW 27 26 5
0x000A          SUBI 16 15
0x000B          ANDI 17 240
0x000C   (b)    CP 16 17
0x000D          BREQR 1

With the (b) maybe written in red or something.

[Flu]

Nobody is currently working on this, so if anybody wants to take it, leave a comment.