Fix find bugs errors and warnings

• BlobOutputStream had uninitialized buffer
• Fix incorrect map key for "get" in TypeMapContext
• PgType.Row equals implements equals/hashCode more correctly
• Throw not implemented instead of returning null in a few method implementations
• Use empty string as "null" in properties and settings (null isn't allowed)
• Removed dead stores
• Removed unused member variables
• Removed redundant code
• Privatized members of Notice