Support customizing emulator port (#383)

* Add port parameter

* Fix a typo in test description

* Fix avd not being started with correct port

* Fix wrong port being used to kill an emulator if there was an exception

__tests__/input-validator.test.ts

@@ -1,4 +1,5 @@
 import * as validator from '../src/input-validator';
+import { MAX_PORT, MIN_PORT } from '../src/input-validator';
 
 describe('api-level validator tests', () => {
   it('Throws if api-level is not a number', () => {
@@ -172,6 +173,33 @@ describe('force-avd-creation validator tests', () => {
   });
 });
 
+describe('emulator-port validator tests', () => {
+  it('Validates if emulator-port is even and in range', () => {
+    const func = () => {
+      validator.checkPort(5554);
+    };
+    expect(func).not.toThrow();
+  });
+  it('Throws if emulator-port is lower than MIN_PORT', () => {
+    const func = () => {
+      validator.checkPort(MIN_PORT - 2);
+    };
+    expect(func).toThrow();
+  });
+  it('Throws if emulator-port is higher than MAX_PORT', () => {
+    const func = () => {
+      validator.checkPort(MAX_PORT + 2);
+    };
+    expect(func).toThrow();
+  });
+  it('Throws if emulator-port is odd', () => {
+    const func = () => {
+      validator.checkPort(5555);
+    };
+    expect(func).toThrow();
+  });
+});
+
 describe('disable-animations validator tests', () => {
   it('Throws if disable-animations is not a boolean', () => {
     const func = () => {