Don't use MIME multipart boundary strings beginning with "-"
Don't use MIME multipart boundary strings beginning with "-"

It apparently triggers a bug in Go's multipart parser.

The leading "-" was introduced in 4/2015 by commit 611dca4a which
changed the prefix in the strings generated by CBLCreateUUID() from a
"!" to a "-".

Fixes #1059

amco/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios