Feature: search messages

resources/icons/search.svg

src/app/constant/JamiStrings.qml

src/app/constant/JamiTheme.qml

src/app/mainview/components/ChatView.qml

src/app/mainview/components/ChatViewHeader.qml

src/app/mainview/components/ContactSearchBar.qml

src/app/mainview/components/DocumentsScrollview.qml

src/app/mainview/components/FilePreview.qml

src/app/mainview/components/MediaPreview.qml

src/app/mainview/components/MessagesResearchPanel.qml

src/app/mainview/components/MessagesResearchView.qml

src/app/mainview/components/Searchbar.qml

src/app/messagesadapter.cpp

src/app/messagesadapter.h

src/libclient/api/conversationmodel.h

src/libclient/conversationmodel.cpp