charmloader: log fails to file

Log all charms and bundles that failed the ingestion process. With err descriptions if possible.
internal/v4: implement debug/status endpoint
Merge branch 'v4' into log-all-loader-fails-to-file
name log file .err not -err
minor fixes for review
actually log
Merge pull request #109 from rogpeppe/050-debug-status

internal/v4: implement debug/status endpoint

As newly documented in the charm store.
Not all entries are implemented yet.
Merge pull request #103 from jrwren/log-all-loader-fails-to-file

charmloader: log fails to file

Log all charms and bundles that failed the ingestion process. With err descriptions if possible.
Ingest bundles
Only digest entities if not present in the charm store.
Better name for bzrDigestKey.
Exclude existing entities in a separate function.
Better code organization and improve digest logging.
Avoid setting the request content length where not required.
Improve doCharmStoreRequest documentation.
Implement charmStoreGet and charmStorePut helper functions.
Merge pull request #111 from frankban/revision-info

Only digest entities if not present in the charm store.

Store the bzr-digest extra-info for all the ingested entities, and compare the value in subsequent charmload calls.
style changes

rename archiveToer -> archiverTo
simplify building reordered BranchTip slice
Merge branch 'v4' of github.com:juju/charmstore into ingest-bundles

Conflicts:
	lppublish/lpad.go
add TODO improve/add control of memory usage