Issue #121 - Add help text popover for command arguments

[bkseto]

This PR adds the ability for users to view command argument information by clicking on the info icon.

Examples:

• SEND_STR_ARG

- !Command
  name:      SEND_STR_ARG
  opcode:    0x0005
  subsystem: CMD
  title: Send string argument value
  desc:      |
    This command tests sending a single string argument.

  arguments:
    - !Argument
      name: str_arg
      desc: String Argument
      units: none
      type: S16
      bytes: [0,15]

• SEQ_ENABLE_DISABLE

- !Command
  name:      SEQ_ENABLE_DISABLE
  opcode:    0x0003
  subsystem: CMD
  title: Enable/Disable Sequence
  desc:      |
    This command enables or disabled the specified sequence.  If a
    sequence to be disabled is currently executing, it will be
    interrupted.

  arguments:
    - !Argument
      name:  sequence_id
      desc:  Sequence ID
      units: none
      type:  MSB_U16
      bytes: [0,1]

    - !Argument
      name:  enable
      desc:  Enable
      units: none
      type:  U8
      bytes: 2
      enum:
        0: DISABLED
        1: ENABLED

• CORE_SET_OP_MODE

- !Command
  name:      CORE_SET_OP_MODE
  opcode:    0x0006
  subsystem: CORE
  desc:      |
    This command sets the operational mode.

  arguments:
  - !Argument
    name:  mode
    desc:  Mode
    units: none
    type:  U8
    bytes: 0
    enum:
      0: SAFE
      1: IDLE
      2: SCANNING
      3: SCIENCE

Note: Most of the popover implementation was borrowed from here.

Closes #121.