Add TestingDirAuthVoteExit option (like TestingDirAuthVoteGuard)

Add the TestingDirAuthVoteExit option, a list of nodes to vote Exit for,
regardless of their uptime, bandwidth, or exit policy.

TestingTorNetwork must be set for this option to have any effect.

Works around an issue where authorities would take up to 35 minutes to
give nodes the Exit flag in a test network, despite short consensus
intervals. Partially implements ticket 13161.
test-network.sh: Use "/bin/echo -n" rather than builtin echo

The default shell on OS X is bash, which has a builtin echo. When called
in "sh" mode, this echo does not accept "-n". This patch uses "/bin/echo -n"
instead.

Partially fixes issue 13161.
Add test-network delay option

Add a --delay option to test-network.sh, which configures the delay before
the chutney network tests for data transmission. The default remains at
18 seconds if the argument isn't specified.

Apparently we should be using bootstrap status for this (eventually).

Partially implements ticket 13161.
Merge branch 'issue-13161-test-network' into issue-13161-integrated-testing
Stop using default authorities with both Alternate Dir and Bridge Authority

Stop using the default authorities in networks which provide both
AlternateDirAuthority and AlternateBridgeAuthority.

This bug occurred due to an ambiguity around the use of NO_DIRINFO.
(Does it mean "any" or "none"?)

Partially fixes bug 13163.
Improve DIRINFO flags' usage comments

Document usage of the NO_DIRINFO and ALL_DIRINFO flags clearly in functions
which take them as arguments. Replace 0 with NO_DIRINFO in a function call
for clarity.

Seeks to prevent future issues like 13163.
Bitwise check BRIDGE_DIRINFO

Bitwise check for the BRIDGE_DIRINFO flag, rather than checking for
equality.

Fixes a (potential) bug where directories offering BRIDGE_DIRINFO,
and some other flag (i.e. microdescriptors or extrainfo),
would be ignored when looking for bridge directories.

Final fix in series for bug 13163.
Merge branch 'bug-13163-AlternateAuthorities-type-handling' into network-integration
Merge branch 'network-integration'