GSQL lexer syntax changes

[gregoryg]

pygmentize was hanging or taking minutes to parse certain GSQL code.

Syntax changes include: adding [], <>, and _ (square brackets, angle brackets and single underscore) to the Punctuation class.
The test for that fix is now include in tests/examplefiles/gsql/test.gsql

A one-liner to test for that fix:
CREATE QUERY tg_astar (VERTEX source_vertex, VERTEX target_vertex, SET<STRING> e_type, STRING wt_type, STRING latitude, STRING longitude,

The string regex was causing backtracking in some cases - simplified here.

In GSQL DDL, parameter such as $0, $"fieldname" and _ to indicate empty position are possible. They were being flagged as errors. The test for that change is also added to the test.gsql file

A one-liner to test the DDL syntax fix:
LOAD Inventory TO EDGE in_warehouse_inventory VALUES($"warehouse", $1, $_)

Reusing edge names for multiple usage requires using pipe as an operator. Pipe is now added to that section.

Test case was added to test.gsql

A one-liner test for edge name reuse :
ADD UNDIRECTED EDGE in_code(FROM City, TO PostalCode | FROM Correspondence, TO PostalCode | FROM Address, TO PostalCode);

[Anteru]

Thanks, that was one nasty case of catastrophic backtracking you fixed there!