Fix bug: DavStorage methods can now work correctly on chrom{e,ium}

On Google Chrome or Chromium, requests methods (POST,PUT,GET,DELETE) act on the
internal browser cache, so important action like PUT could not work.
The Url sended with the request is appended by '?_=xxx' (which 'xxx' is the
current date in ms) to make this Url unique.

OfficeJS/src/jio.storage/davstorage.js

@@ -79,12 +79,12 @@ var newDAVStorage = function ( spec, my ) {
     priv.putOrPost = function (command,type) {
 
         var secured_docid = priv.secureDocId(command.getDocId());
-
         $.ajax ( {
             url: priv.url + '/' +
                 priv.secured_username + '/' +
                 priv.secured_applicationname + '/' +
-                secured_docid,
+                secured_docid + '?_=' + Date.now(), // to make url unique!
+                // and avoid chrome PUT on cache !
             type: type,
             data: command.getDocContent(),
             async: true,
@@ -128,7 +128,7 @@ var newDAVStorage = function ( spec, my ) {
                 url: priv.url + '/' +
                     priv.secured_username + '/' +
                     priv.secured_applicationname + '/' +
-                    secured_docid,
+                    secured_docid + '?_=' + Date.now(),
                 type: "GET",
                 async: true,
                 dataType: 'text', // TODO is it necessary ?
@@ -164,7 +164,7 @@ var newDAVStorage = function ( spec, my ) {
             url: priv.url + '/' +
                 priv.secured_username + '/' +
                 priv.secured_applicationname + '/' +
-                secured_docid,
+                secured_docid + '?_=' + Date.now(),
             type: "PROPFIND",
             async: true,
             dataType: 'xml',
@@ -219,7 +219,7 @@ var newDAVStorage = function ( spec, my ) {
                 url: priv.url + '/' +
                     priv.secured_username + '/' +
                     priv.secured_applicationname + '/' +
-                    priv.secureDocId(file.id),
+                    priv.secureDocId(file.id) + '?_=' + Date.now(),
                 type: "GET",
                 async: true,
                 dataType: 'text', // TODO : is it necessary ?
@@ -246,7 +246,7 @@ var newDAVStorage = function ( spec, my ) {
             $.ajax ( {
                 url: priv.url + '/' +
                     priv.secured_username + '/' +
-                    priv.secured_applicationname + '/',
+                    priv.secured_applicationname + '/' + '?_=' + Date.now(),
                 async: true,
                 type: 'PROPFIND',
                 dataType: 'xml',
@@ -339,12 +339,11 @@ var newDAVStorage = function ( spec, my ) {
     that.remove = function (command) {
 
         var secured_docid = priv.secureDocId(command.getDocId());
-
         $.ajax ( {
             url: priv.url + '/' +
                 priv.secured_username + '/' +
                 priv.secured_applicationname + '/' +
-                secured_docid,
+                secured_docid + '?_=' + Date.now(),
             type: "DELETE",
             async: true,
             headers: {'Authorization':'Basic '+Base64.encode(