Binary read support for Ion 1.1 scalars

[zslayton]

Support parsing the new encodings for:

• [x] Nulls - #766
• [x] Bools - #753
• [x] Ints - #754
• [x] Floats - #756
• [x] Decimals - #757
• [x] Timestamps - #765
• [x] Strings - #754
• [x] Symbols - #758
• [x] Blobs - #755
• [x] Clobs - #755

[nirosys]

Base reader PR: #737