Improve support for non-ASCII characters in variable names
Currently, Sparql.js uses a regex which allows all non-ASCII characters (in the
basic multilingual plane) that are allowed by the SPARQL specification.
Elsewhere in the code, such as in the query helper, a regex which only accepts
basic ASCII is used.
This extracts the information about what consistitutes a valid variable name
from Sparql.js into a separate file, which has three varibles and one function:
- VariablePattern, a regex pattern for a valid variable
- PrefixPattern, a regex pattern for a valid prefix
- ValidCharacters, a regex pattern for any character valid in a variable name
- makeVariableName(), which takes a string and returns a valid variable
and then updates the files to use these new functions and variables.