Instead of using a fixed 100x30 window size query the operating system
for the exact size, also fixes a bug where the last line before calling
the pager is repeated twice.
New config "tab" allows user to set a string instead of literal tab
(e.g. "... ").
New config "source-list-tab-color" allows that string to be colored.
This builds on top of the `updateColorScheme` change
For commands that could produce large amounts of output switch to a
pager command ($DELVE_PAGER, $PAGER or more) after a certain amount of
output is produced.
Fixes#919
