AdHocFilters: add simple text-based operators to OPERATORS

[eskirk]

to help simplify the use of the AdHocFilters to a less technical audience, it would be helpful if we included some "text based" operators to the list of possible operators such as:

• contains
• startsWith
• endsWith
• etc.

this would help simplify discovery in many of our scenes apps where it is cumbersome to need to write a regex expression when we could abstract that away from the user and allow them to simply focus on data exploration.