refactor temp_buffer to saved_primary_buffer
refactor temp_default_char to primary_default_char
save the Alt buffer when restoring primary buffer
refactor restoreBuffer to showPrimaryBuffer
add showAltBuffer and showingAltScreen showAltBuffer replaces saveBuffer for showing the alt term screen showAltBuffer saves a copy of the alt screen for later display showPrimaryBuffer sets and respects boolean showingAltScreen
refactor saveBuffer to savePrimaryBuffer
respect boolean showingAltScreen throughout instead of checking saved_primary_buffer for content
wipe the alt screen if the primary screen resizes
doc/comment
Remove some duplicated code