Fix test result summary to only count succeeded and failed assertions

The .test-result files also contains the diff and for failures all diff
lines were counted. Now only lines containing "[OK]" or "[FAIL]" are
counted.
Add test option to start tig inside a debugger
Move repo setup method from main/show-changes-test to libgit
Reorder test directory setup and TEST_OPTS parsing
Add test option to show tig trace information
Partly restore old refresh behavior

This ensures that the current view is refreshed after returning from an
external command when `refresh-mode` is set to `after-command`. That was
what Tig used to do before the option was introduced. It special cases
the 'after-command' event to force a refresh in the current view.

The fix is tested to work in both the main and status view.

Fixes #289
Unify the color palette used for graph and ID drawing

Graph rendering will now use up to 14 colors if the terminal supports
boldified (highlighted) colors.

References #305