Make context size and screen clearing configurable

[tuxx42]

• the number of lines of the context can be configured indepdentantly for the code and stack context (this can be nice on high resolution screens)
• the screen clearing can be disabled using a config switch (screen clearing can be disabled, allowing a scrollback buffer to compare to previous states)

[tuxx42]

let me know if I should split this into two seperate pull requests

[longld]

I merged the idea of screen clearing in https://github.com/longld/peda/commit/847a926b04e6580629db33f629f4431744e2de1b

[elklepo]

@tuxx42 do You plan to resume this PR? I'd love to see this changes on main branch.