Update help_text to display actual keybinds

[enzalito]

I tried to do it i a way that does not bring lots of changes to the code. I restrained myself from using Keybindings::help_entries to generate everything as I wasn't sure about what you had planned.

Most of the entries are the exact same, i adapted a few of them. For example:

s          Filter outline headings (Esc: clear, Enter: keep)

is now:

s          Filter outline headings
Esc        Clear search
Ret        Confirm search

[nicholasjpaterno]

@enzalito same as PR #46 these look good for the most part, I'm going to make one tiny fix upstream after its merged but these are addressing bugs so lets get this merged asap! Thanks for your contributions!