Update regex for sql-name (#163)

* Update regex for sql-name

* Update input/fsh/models.fsh

Allow single-character names

* Update input/fsh/models.fsh

Allow single-character names

input/fsh/models.fsh

@@ -1,13 +1,13 @@
 Invariant: sql-name
 Description: """
 Name is limited to letters, numbers, or underscores and cannot start with an
-underscore -- i.e. with a regular expression of: ^[^_][A-Za-z][A-Za-z0-9_]+$ 
+underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ 
 
 
 This makes it usable as table names in a wide variety of databases.
 """
 Severity: #error
-Expression: "empty() or matches('^[^_][A-Za-z][A-Za-z0-9_]+$')"
+Expression: "empty() or matches('^[A-Za-z][A-Za-z0-9_]*$')"
 
 
 Invariant: sql-expressions

input/ignoreWarnings.txt

@@ -4,5 +4,8 @@
 # (And include comments like this justifying why)
 # See https://github.com/FHIR/sample-ig/blob/master/input/ignoreWarnings.txt for examples
 
-# Potential publisher bug?
-Error in constraint 'sql-expressions' with expression '(path | forEach | forEachOrNull | union).count() = 1': Cannot assign field "sourceDefinition" because "res" is null
+# Publisher bug?
+Error in constraint 'sql-expressions' with expression '(path | forEach | forEachOrNull | union).count() = 1': Cannot assign field "sourceDefinition" because "res" is null
+
+# Not a real HL7 project
+When HL7 is publishing a resource, the owning committee must be stated using the http://hl7.org/fhir/StructureDefinition/structuredefinition-wg extension