Revert "Migrate errors to TypeScript"

This reverts commit ab906faa17.

src/errors.ts

@@ -1,51 +0,0 @@
-// can't just do InvalidStoreError extends Error
-// because of http://babeljs.io/docs/usage/caveats/#classes
-export function InvalidStoreError(reason: string, value: boolean): void {
-    const message = `Store is invalid because ${reason}, ` +
-        `please stop the client, delete all data and start the client again`;
-    const instance = Reflect.construct(Error, [message]);
-    Reflect.setPrototypeOf(instance, Reflect.getPrototypeOf(this));
-    instance.reason = reason;
-    instance.value = value;
-    return instance;
-}
-
-InvalidStoreError.TOGGLED_LAZY_LOADING = "TOGGLED_LAZY_LOADING";
-
-InvalidStoreError.prototype = Object.create(Error.prototype, {
-    constructor: {
-        value: Error,
-        enumerable: false,
-        writable: true,
-        configurable: true,
-    },
-});
-Reflect.setPrototypeOf(InvalidStoreError, Error);
-
-export function InvalidCryptoStoreError(reason: string): void {
-    const message = `Crypto store is invalid because ${reason}, ` +
-        `please stop the client, delete all data and start the client again`;
-    const instance = Reflect.construct(Error, [message]);
-    Reflect.setPrototypeOf(instance, Reflect.getPrototypeOf(this));
-    instance.reason = reason;
-    instance.name = 'InvalidCryptoStoreError';
-    return instance;
-}
-
-InvalidCryptoStoreError.TOO_NEW = "TOO_NEW";
-
-InvalidCryptoStoreError.prototype = Object.create(Error.prototype, {
-    constructor: {
-        value: Error,
-        enumerable: false,
-        writable: true,
-        configurable: true,
-    },
-});
-Reflect.setPrototypeOf(InvalidCryptoStoreError, Error);
-
-export class KeySignatureUploadError extends Error {
-    constructor(message: string, public value: { failures: any }) { // TODO: types
-        super(message);
-    }
-}