Add support for LIKE expressions to JEP parser

[Nicklas Nordborg]

It would for example be useful to create filters like: rep('symbol') == 'BRCA%'.

But since the parsing of operators in JEP is rather fixed we probably have to define a custom function: like(rep('symbol'), 'BRCA%')

[Nicklas Nordborg]

I think it would be possible to detect if a '%' is present in the right-hand argument in the filter string and then use LIKE in the SQL expression instead of ==. It will break existing expressions that search for an explicit '%' but they could be re-written as: 'BRCA%' == rep('symbol')

[Nicklas Nordborg]

(In [5401]) Fixes #1504: Add support for LIKE expressions to JEP parser

The parse will detect situations were the right hand argument of expressions like foo == 'bar%' is a string constant that includes a '%'. If so, the parser will create a LIKE-restriction instead of an EQUALS-restriction.