Invalidate an independent variable 'value' given as a range of numbers

[GraemeWatt]

Related to HEPData/hepdata-converter#41, some records have an incorrect YAML encoding such as value: 800 - 1000 (table) or value: '1-1.5' (table) instead of separate low and high values. Such an incorrect YAML encoding gives an acceptable table rendering and is properly handled by the visualisation code, so it could easily be missed in the review process. We should therefore invalidate cases where an independent variable value (without low and high values) has the form of two numbers separated by a hyphen (with or without surrounding spaces). This might be possible using the not keyword in the JSON schema. Note that the numbers might be given in scientific notation. If value takes the form of two numbers separated by a hyphen, an error message should be returned asking the user to instead give the range as low and high values.

[alisonrclarke]

Note that the numbers might be given in scientific notation.

Can I check which formats you mean for this? Do you just programming-style formats e.g. 1.3e7 or 4.2E-9?