Create regular expression to match enzyme codes

[cthoyt]

Also test it against many examples.

• Ones with dashes: 1.2.3.-
• Ones that skip trailing dashes: 1.2.3
• Ones with two digits 1.12.5

Fail on ones whose first number isn't 1-6

• 7.1.2.5 is invalid

What about alternative formats where they use stars as wildcards?

For example: See

CHEBI:76878 which is labeled EC 2.3.1.* (acyltransferase transferring other than amino-acyl group) inhibitor