term: rework color cutomizing

term: rework color cutomizing

* term.el (term-handle-colors-array): Use a set of new faces to
color the terminal.  Also uses :inverse-video property.
(term-default-fg-color): Set to nil by default, deprecate in favor
of `term-face'.
(term-default-bg-color): Set to nil by default, deprecate in favor
of `term-face'.
(term-current-face): Use `term-face' by default.
(term-bold-attribute): Variable deleted.