docfixes (brevity), and document ``length``
move setupterm() prior to the setting of _CUR_TERM

THis resolves a rare issue: failing to instantiate a Terminal() instance with an illegal ``kind`` value. Then, any subsequent instantiation would *not* return capabilities of "the prior kind", but the warning would tell you so.
use TestTerminal instead of Terminal()
fix missing @as_subprocess
proper pattern for multi-sequence capability vals

for terminal capabilities such as 'clear' or 'normal' that may be multiple sequences, now split them by \x1b, and evaluate the sum total, or any boolean result, for the evaluation of is_movement or unprintable_length.
now test many kinds of terminal ``kind``s!

Don't you wish we could have always done this :-)

of course, until I implement a complete _init_sequence_patterns(), some tests are failing (particularly on the 'screen' kind).