Continue discovery on connect errors (fixes #324)

Continues trying to connect to the discovery server at regular intervals despite
failure. Whether or not to retry and retry interval should be specified in
configuration (not currently in this fix).
incomingIndexes should not be a package variable (fixes #344)
Revert "Add temporary debug logging for #344 (revert later)"

This reverts commit 5353659f9fcb840142ba4c8d83f48654d43d4bdc.
Handle WANPPPConnection devices (fixes #431)
Improve protocol & leveldb debugging
Merge branch 'v0.8'

* v0.8:
  Handle WANPPPConnection devices (fixes #431)
  Revert "Add temporary debug logging for #344 (revert later)"
  incomingIndexes should not be a package variable (fixes #344)
  Continue discovery on connect errors (fixes #324)

Conflicts:
	files/set.go
	model/model.go
	protocol/protocol.go
Hand incoming indexes on main goroutine (this should be fine now)
LocalVersion can move backwards as well as forwards