CB-7843 Fixes angular routing on WP8

(cherry picked from commit e693d147b87641fcc2f341dbea7bc7c73d14f9e1)
CB-7892 XHR to local files poly should only load/run once

(cherry picked from commit 6bb3fc38a4d67cf378e1b11839c4af327ebfccd5)
Adding fixes to XHRHelper class to successfully work with Angular JS.

- Cordova RTC work item number: 60654
- Apache Cordova Jira issue:
https://issues.apache.org/jira/browse/CB-7843,
https://issues.apache.org/jira/browse/CB-7892
- Markmail or Google Group reference: n/a
- Product PMR: 65567,650,758
- APAR: PI31953 - Item 60655
- Cherry-pick: e693d147b87641fcc2f341dbea7bc7c73d14f9e1,
6bb3fc38a4d67cf378e1b11839c4af327ebfccd5
- Description: Main issue is that the window.__XHRShimAliases object
gets recreated when window location changes, causing that callbacks for
XHR calls
are never getting received. A condition was added to define if the
object is already present, and avoid unnecessary recreation.
The last one was added to fix an angular use case, to avoid reload on
InjectScript Method when the url is changed.