RELEASE 2.9.0: Misc Small PRs

Adds:

hg: print log from most recent to oldest, so don't truncate current commit
#356

even if there are no memcached servers, DoNotCache results are unwrapped
#361

minor fixes (test_solver)
#370

fix for TestRelease.test_2_variant_add
#371

invalidate memcache if a package file has been deleted / moved / etc
#376

add max_package_changelog_revisions config option
#357

allow configuration of truncate cap for shell error output
#363

added option to force color output, even if not a tty
#365