Paging improvements

[bmatsuo]

Paging content should be easier and more prevalent. As more documentation becomes available through the ":help" command documentation should be paged in the same fashion as jq output.

It should also be possible to specify a pager, either through the PAGER environment variable or potentially a config file. The concern I have over using PAGER is that, at least the way I see things, the system default pager is not necessarily suited for jqsh. Quick example, I usually like less to clear paged content from the terminal after exiting but this is not the behavior I want in jqsh. The behavior I want in jqsh is closer to more.