Previously, recursion overrides were only available by setting
a numeric 'depth' value in a DEPS file.  This meant that it
was not possible to control recursion per-dependency entry.

This change adds a recurselist variable with a list structure.
If a named dependency is present in the list, then gclient will
recurse into that dependency's DEPS.

As part of this change, I move the recursion controls off of
DependencySetting and onto Dependency.  The new setup of being
based on Dependency allows access to the dependency's name.

The controls are only called from Dependency instances.  They
have always needed access to self.parent (in the Dependency
context), so this should be more correct than the previous setup.

BUG=390246

Review URL: https://codereview.chromium.org/331373009

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@280690 0039d316-1c4b-4281-b951-d872f2087c98