misc: implement update system

- re-introduce a genericized NetworkManager
- isolate update logic into a qml accessible class derived from
  NetworkManager
- fix QtWebEngineProcess missing when re-installing over existing
  version
- provide a command line option to override the base url
  for testing local and remote updates
- clean-up manual update-check UI

Gitlab: #101
Change-Id: I9c8d2badae59ec31cab12d38b8470edf2bcad401
diff --git a/jami-qt.pro b/jami-qt.pro
index d3933c6..762114c 100644
--- a/jami-qt.pro
+++ b/jami-qt.pro
@@ -111,7 +111,9 @@
 
 # Input
 HEADERS += \
+        src/networkmanager.h \
         src/smartlistmodel.h \
+        src/updatemanager.h \
         src/utils.h \
         src/bannedlistmodel.h \
         src/version.h \
@@ -159,7 +161,9 @@
 SOURCES += \
         src/bannedlistmodel.cpp \
         src/accountlistmodel.cpp \
+        src/networkmanager.cpp \
         src/runguard.cpp \
+        src/updatemanager.cpp \
         src/webchathelpers.cpp \
         src/main.cpp \
         src/smartlistmodel.cpp \