Updated requestFileSystem, set app workspace path as fs.root.fullPath

1. FileExec and spec tests will be added later.
Added FileExec for file plugin, and changed cordova/exec to FileExec in DirectoryEntry and Entry

1. Added FileExec for file plugin, and changed cordova/exec to FileExec
in DirectoryEntry and Entry
2. Spec tests will be added later
Added support for DirectoryReader,FileEntry,FileReader,FileWriter in FileExec
Updated resolveLocalFileSystemURI, if entry.fullPath in not under app workspace, then return SECURITY_ERR
Added spec tests for file exec

1. Added spec tests for file exec
2. Fixed bugs found by spec tests
Optimized the implementation of getParent, and changed the directory entry's name from "Documents" to "workspace"
Rename file-workspace.tests.js to file.xface.tests.js
[doing-183]Added xface auto tests for file plugin
C:/Users/YTB/AppData/Local/Temp/somedir is should valid path uri
add description to autotest(file.spec.105)