(core) Add rules to eslint to better match our coding conventions.

Summary:
We used tslint earlier, and on switching to eslint, some rules were not
transfered. This moves more rules over, for consistent conventions or helpful
warnings.

- Name private members with a leading underscore.
- Prefer interface over a type alias.
- Use consistent spacing around ':' in type annotations.
- Use consistent spacing around braces of code blocks.
- Use semicolons consistently at the ends of statements.
- Use braces around even one-liner blocks, like conditionals and loops.
- Warn about shadowed variables.

Test Plan: Fixed all new warnings. Should be no behavior changes in code.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2831

app/common/GranularAccessClause.ts

@@ -78,7 +78,7 @@ export interface UserAttributeRule {
  * Check some key facts about the formula.
  */
 export function getFormulaProperties(formula: ParsedAclFormula) {
-  const result: FormulaProperties = {}
+  const result: FormulaProperties = {};
   if (usesRec(formula)) { result.hasRecOrNewRec = true; }
   const colIds = new Set<string>();
   collectRecColIds(formula, colIds);