terminal-emulator: changes + check-sr-results hook

- test-terminal-emulator.sh proposed changes implemented,
  check-sr-results.py now has a hook for terminal-emulator.sh.
- Added dependency information about terminal-emulator and
  a description/usage paragraph.
- All non UTF-16 files are emulated and saved to a temporary
  file which is used by check_file_contains and if_contains.
- Cleanup_line is replaced by remove_control_characters to
  improve success rate of handling control characters.

Signed-off-by: Abhi Singh <Abhi.Singh@arm.com>