contactpicker: fix margin and label

Change-Id: Idcbefba3765932eb673f3416bf59fdd16e2e3c1d
GitLab: #621

src/constant/JamiStrings.qml

@@ -212,6 +212,7 @@ Item {
     property string resumeCall: qsTr("Resume call")
     property string pauseVideo: qsTr("Pause video")
     property string resumeVideo: qsTr("Resume video")
+    property string addParticipant: qsTr("Add participant")
     property string addParticipants: qsTr("Add participants")
     property string chat: qsTr("Chat")
     property string moreOptions: qsTr("More options")

src/mainview/components/ContactPicker.qml

@@ -94,12 +94,11 @@ Popup {
                 id: contactPickerContactSearchBar
 
                 Layout.alignment: Qt.AlignCenter
-                Layout.topMargin: 5
-                Layout.bottomMargin: 5
-                Layout.preferredWidth: implicitWidth
+                Layout.margins: 5
+                Layout.fillWidth: true
                 Layout.preferredHeight: 35
 
-                implicitWidth: contactPickerPopupRect.width - 10
+                placeHolderText: JamiStrings.addParticipant
 
                 onContactSearchBarTextChanged: {
                     ContactAdapter.setSearchFilter(text)

src/mainview/components/ContactSearchBar.qml

@@ -31,6 +31,7 @@ Rectangle {
     signal returnPressedWhileSearching
 
     property alias textContent: contactSearchBar.text
+    property alias placeHolderText: contactSearchBar.placeholderText
 
     function clearText() {
         contactSearchBar.clear()