variable-name rule should ignore identifiers which represent constructors

[adidahiya]

This will require invoking the type checker. It should address #457.

Proposal

Rule walkers can get a TypeChecker via languageService.getProgram().getTypeChecker(). This object should be saved as a private member of the walker class (similar to what we do for languageService in NoUnusedVariablesWalker).

VariableNameWalker#handleVariableName should check if the given identifier is a constructor and return early if it is.

utils.ts should get a new function called isTypeFlagSet which does something similar to isNodeFlagSet, but for type flags.

[adidahiya]

see here for how to use the type checker: https://github.com/Microsoft/tslint-microsoft-contrib/blob/1bb87a93860ed8450b0962cf947cc8c4a89437ee/src/AstUtils.ts

[adidahiya]

seems like people are doing fine with pascal case. closing this.