extra/runner summary report: Fix display of 100% in confidence interval

This displays "100%" instead of "1.0e+2%".

Note that the original code (in the "else" branch) is correct; only the
edge cases for k=0 and k=n (that I introduced in 2c333020) were
incorrect.
extra/pylint.{sh,conf}: Cleanup: Move "ignored-classes" to config file

The ignored checkers/messages are specified in the config file, so the
ignored classes belong there too.
make check: Disable pylint checks on numpy members

It seems that pylint can't figure out some magic done by numpy 1.8.0,
so stbt.py would fail `make check` with:

    E1101:410,16:detect_motion: Module 'numpy' has no 'multiply' member
    E1101:411,20:detect_motion: Module 'numpy' has no 'ones' member
    E1101:411,50:detect_motion: Module 'numpy' has no 'uint8' member
    E1101:413,26:detect_motion: Module 'numpy' has no 'uint8' member
    E1101:1013,11:gst_to_opencv: Module 'numpy' has no 'ndarray' member
    E1101:1018,14:gst_to_opencv: Module 'numpy' has no 'uint8' member
    E1101:1096,9:_match_template: Module 'numpy' has no 'ones' member
    E1101:1096,59:_match_template: Module 'numpy' has no 'zeros' member
    E1101:1099,18:_match_template: Module 'numpy' has no 'float32' member
    E1101:1161,39:_match_template: Module 'numpy' has no 'uint8' member
    E1101:1277,22:_log_image: Module 'numpy' has no 'float32' member
    E1101:1988,24:_fake_frames_at_half_motion.FakeDisplay.frames: Module 'numpy' has no 'zeros' member
    E1101:1988,53:_fake_frames_at_half_motion.FakeDisplay.frames: Module 'numpy' has no 'uint8' member
    E1101:1989,24:_fake_frames_at_half_motion.FakeDisplay.frames: Module 'numpy' has no 'ones' member
    E1101:1989,52:_fake_frames_at_half_motion.FakeDisplay.frames: Module 'numpy' has no 'uint8' member

These are genuine numpy members (I tried them all in ipython).

Pylint 1.0.0 and 0.28.0 both fail to understand numpy 1.8.0. I didn't
have this problem with earlier versions of numpy (1.6.2, at least).
api-doc.sh: Raise error if command line argument is missing

api-doc.sh expects a command line argument that it passes to `cat`.

If no command line argument is specified, `cat` hangs the execution
waiting for standard input, while the user of the script may think that
documentation is being generated.
stbt.press: Ensure minimum delay between subsequent key presses

Our usual way of ensuring that remote control keys are pressed at
the right time is:

stbt.press(key1)
stbt.wait_for_match(template)
stbt.press(key2)

Due to the enhanced template match algorithm introduced in commit
ac97d6dd, wait_for_match might return so fast that some set-top-boxes
miss the second key press. According to our measurement results
these set-top-boxes require a certain minimum delay between subsequent
key presses in order to register every key.

This commit adds a new optional parameter `interpress_delay_secs` to
`stbt.press` that specifies a minimum time to wait after the preceding
key press that `stbt.press` ensures. The default value of this parameter
is read from the parameter of the same name in the `[press]` section of
the stbt config file.
tests for stbt.press interpress delay read config from tests/stbt.conf

The pattern used by all these tests is to use a `$STBT_CONFIG_FILE` (set
by `tests/run-tests.sh` to `tests/stbt.conf`) that contains the same
defaults as `tests/../stbt.conf`. This is necessary because
`$STBT_CONFIG_FILE` overrides the user's
`~/.config/stbt/stbt.conf` (which has configuration outside of our
control, that could break the tests).

This commit makes `test_that_press_waits_between_subsequent_presses` and
`test_that_press_reads_default_delay_from_stbt_conf` use the same
pattern used by all the other tests. Otherwise, the user's configuration
might have a "source_pipeline" that doesn't work, and thus causes
`stbt-run` to fail.
tests: Add test_that_press_doesnt_wait_any_longer_than_necessary
Merge branch 'interpress-delay'

* interpress-delay:
  tests: Add test_that_press_doesnt_wait_any_longer_than_necessary
  tests for stbt.press interpress delay read config from tests/stbt.conf
  stbt.press: Ensure minimum delay between subsequent key presses