WIP 1
WIP 2: rest of the data types, rest of syntax note types
WIP 3 TokenSink
02-element.t, initial bugfixes
D'oh, repeat_sep is a >4010ism and needs to be optional
Misc fixes for data type encoder
s/SyntaxNote/Constraint/g, add a (for now informative) incomplete attribute to segments
WIP 1 schema parser
Split Segment from SegmentUse to better match the schema
Misc fixes; start test for parser
Test successful parser function
WIP 1 TokenSource
Initial working version of, tests for, TokenSource
Use ISA version number to interpret ISA
Add segment counter to sink, record charset
Enforce more constraints for string values
Move segment towards being stricter about presence versus data, add tests
Start new error handling, segment tests
Refactor Element::encode into a bunch of methods
Add and test datatype parsers