CB-7284 Improve File plugin for windows platform compatibility with current API specs

Fixes multiple spec tests errors [CB-7284](https://issues.apache.org/jira/browse/CB-7284)

Full list of changes:

FileProxy:
* Adds removal of trailing slashes for incoming native paths since Windows threat them as illegal
* Combine getMetadata and getFileMetadata into one method (this fixes multiple metadata spec tests)
* Adds private routine for creating Filesystem instance for Entry from full path to Entry (getFilesystemFromPath)
* Adds filesystem parameter specification for all constructed instances of Entry, FileEntry and DirectoryEntry classes
* Fixes readAsBinaryString method to return true binary string instead of unicode string
* Adds support for slicing to readAsBinaryString and readAsArrayBuffer methods
* Fix removeRecursively method to disallow root directory removal
* Remove multiple usages of createFileQuery and createFolderQuery which is unsupported on Windows Phone 8.1

DirectoryEntry:
* Adds additional check for nativeURL is not undefined/null in DirectoryEntry constructor

Entry:
* Update copyTo and MoveTo methods with proper usage of entry.filesystem in success callbacks (was entry.filesystemName earlier, but Entry class don't have filesystemName property)

resolveLocalFileSystemURI:
* Update resolveLocalFileSystemURL method with proper usage of entry.filesystem in success callbacks (was entry.filesystemName earlier, but Entry class don't have filesystemName property)
* Adds additional check for leading slash in provided path at resolveLocalFileSystemURL method (since failure of file.spec.12 window.resolveLocalFileSystemURI should error (ENCODING_ERR) when resolving invalid URI with leading /.)


This also includes fix for getMetadata method from https://github.com/apache/cordova-plugin-file/pull/56