feat(log-viewer): change line count default to 100 and add a since parameter (#2377)

* chore(log-viewer): add the ability to use`since` parameter #1942

https://github.com/portainer/portainer/issues/1942#issuecomment-430246378

* chore(log-viewer): change lineCount to 100 #1942

https://github.com/portainer/portainer/issues/1942#issuecomment-430246378

* fix(log-viewer): js syntax typo for `;` and `'`

forget to lint the code, reported by codeclimate

* fix(log-viewer): use mementjs to format timestamp

1. use moment lib instead of define a function in filter.js(not the right place for this function, removed)
2. set sinceTimestamp init value to `24 hours ago`, as we just need to focus on the relative latest logs after the log-viewer loading, not all the logs(to speedup the process)
3. use moment().unix() to convert the `sinceTimestamp`  to local unix timestamp(not utc)

* chore(log-viewer): add the ability to select the datetime for `since`

* chore(log-viewer): add the ability to fetch logs from specific time

app/docker/components/log-viewer/log-viewer.js

@@ -5,6 +5,7 @@ angular.module('portainer.docker').component('logViewer', {
     data: '=',
     displayTimestamps: '=',
     logCollectionChange: '<',
+    sinceTimestamp: '=',
     lineCount: '='
   }
 });

app/docker/components/log-viewer/logViewer.html

@@ -35,6 +35,17 @@
                </label>
             </div>
           </div>
+          <div class="form-group">
+            <label for="logs_since" class="col-sm-1 control-label text-left">
+              Fetch
+            </label>
+            <div class="col-sm-2">
+              <select class="form-control" ng-model="$ctrl.sinceTimestamp" id="logs_since">
+                <option selected value="">All logs</option>
+                <option ng-repeat="dt in $ctrl.state.availableSinceDatetime" ng-value="dt.value" title="{{ dt.value }}">{{ dt.desc }}</option>
+              </select>
+            </div>
+          </div>
           <div class="form-group">
             <label for="logs_search" class="col-sm-1 control-label text-left">
               Search

app/docker/components/log-viewer/logViewerController.js

@@ -3,6 +3,12 @@ angular.module('portainer.docker')
 function (clipboard) {
 
   this.state = {
+    availableSinceDatetime: [
+      { desc: 'Last day', value: moment().subtract(1, 'days').format() },
+      { desc: 'Last 4 hours', value: moment().subtract(4, 'hours').format() },
+      { desc: 'Last hour', value: moment().subtract(1, 'hours').format() },
+      { desc: 'Last 10 minutes', value: moment().subtract(10, 'minutes').format() }
+    ],
     copySupported: clipboard.supported,
     logCollection: true,
     autoScroll: true,