nearly there with conversion of source_tree
convert keys to source names
100% conversion to sources
IT IS COMPLETE
TO_MERGE
merge comments
Removed r_sources() schema method
SQLT parser now calls _resolve_deps() in schema

The original _resolve_deps logic is now called in the SQLT Parser, but
it is now located in Schema, and the replacement _get_deps has been
removed. This is an intermediate for the final structure, but at least
now all tests pass again (the _get_deps() implementation caused deploy
tests to fail)
_resolve_depth() returns meta data hash vals instead of '1'

Instead of simply returning '1' in the hash value for dependencies, a
hashref is returned with the following meta data attrs:

 depth: number of levels deep the dependency is (i.e. dependencies of
  dependencies). Starts a '0' for direct deps

 for_view: 1 if the dependency is of a ResultSource::View, 0 if it is a
  dependency of of a normal ResultSource table. This option is a topic
  of debate and may be removed/modified
source_tree() now accepts hashref or hashref-as-list
Prelim POD for source_tree()
source_tree() no longer has any options

Per riba on IRC today: "let's lose the option stuff for now entirely"
source_tree() now includes view deps w/ 'is_view' attr

The structure returned by $schema->source_tree() now includes sources
that are virtual views (ResultSource::View) which are indicated by
is_view => 1. Note that dependencies for views themselves are currently
still excluded (which means 'for_view' will always be 0)