Consolidate and reuse pager code for inline console docs

[wvu]

This offers increased readability with the command help near the prompt. Taking the pager approach presently.

• Type help
• See available msfconsole commands without scrolling up
• Type help repeat or help jobs
• See available repeat or jobs options near the prompt

A pager approach is also an option (@acammack-r7), but I think this can be an easy win for me and @wchen-r7. Thoughts welcome.

msf5 > help repeat
Repeat
======

The `repeat` command repeats one or more console commands for a fixed number of
times, a certain length of time, or forever. The repeat command is most useful
for repeating module runs like memory dumpers or scanners that have a random
element to them.

Usage
-----

### Flags

#### -t, --time SECONDS

Start the list of commands until the number of seconds has elapsed.

#### -n, --number TIMES

Start the list of commands a fixed number of times.

#### -h, --help

Display the help banner.



Examples
--------

Run the heartbleed module every 10 seconds against a server for an hour:

    msf5 > use auxiliary/scanner/ssl/openssl_heartbleed
    msf5 auxiliary(scanner/ssl/openssl_heartbleed) > set ACTION DUMP
    # Set other options...
    msf5 auxiliary(scanner/ssl/openssl_heartbleed) > repeat -t 3600 run; sleep 10


Usage: repeat [OPTIONS] COMMAND...
Repeat (loop) a ;-separated list of msfconsole commands indefinitely, or for a
number of iterations or a certain amount of time.

    -t, --time SECONDS               Number of seconds to repeat COMMAND...
    -n, --number TIMES               Number of times to repeat COMMAND..
    -h, --help                       Help banner.
msf5 >

#11407, #11498

[jrobles-r7]

Is this PR delayed?

[acammack-r7]

No, although I would rather not make the output less like man(1). As a note, you can skip the markdown entirely by doing repeat -h.

[wvu]

I'm moving and refactoring my pager code from the developer dispatcher into the dispatcher shell this morning, and we'll see how it looks after that. Output that's closer to man(1) is a good thing.

Our primary gripe is that you can't suppress the Markdown output for msfconsole help, @acammack-r7. This is where the conversation started. The individual commands are less of an issue.

msf5 > help -h
[-] No such command
msf5 > help help
There's only so much I can do
msf5 >

While we could add -h to help, I think the pager approach is better and more correct. less(1) does something similar for its own help.

[acammack-r7]

msf5 > repeat -h
Usage: repeat [OPTIONS] COMMAND...
Repeat (loop) a ;-separated list of msfconsole commands indefinitely, or for a
number of iterations or a certain amount of time.

    -t, --time SECONDS               Number of seconds to repeat COMMAND...
    -n, --number TIMES               Number of times to repeat COMMAND..
    -h, --help                       Help banner.

[wvu]

This is a little too niche of barely a problem for me to be willing to solve right now. Portable pager invocation is not something I want to deal with at the moment, and there are bigger fish to fry.

Someone else can take a stab at this if they'd like. Thanks.