Preserve ContextExtension items order in JSON encoding

[greenhat]

Add tx ids in tx id error on JSON parsing.

Close #685

[coveralls]

Pull Request Test Coverage Report for Build 4114114465

• 3 of 8 (37.5%) changed or added relevant lines in 3 files are covered.
• 17 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.06%) to 63.414%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ergotree-ir/src/chain/json/ergo_box.rs	0	1	0.0%
ergo-lib/src/chain/json/transaction.rs	0	4	0.0%

Files with Coverage Reduction	New Missed Lines	%
ergo-rest/src/api/peer_discovery_internals/non_chrome.rs	2	73.28%
ergotree-ir/src/chain/token.rs	5	72.58%
ergotree-ir/src/serialization/types.rs	10	80.77%

Totals
Change from base Build 4113784281:	-0.06%
Covered Lines:	10091
Relevant Lines:	15913

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💛 - Coveralls