facebook: remove the featute from the code base

Remove from:
- unit tests
- desktop widgets
- preferences
- core intergration
- cmakefiles
- build scripts
- icons
- docs

Also remove the plugins and social network integration.

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>

packaging/android/build.sh

@@ -419,7 +419,6 @@ cmake $MOBILE_CMAKE \
 	-DNO_PRINTING=ON \
 	-DNO_USERMANUAL=ON \
 	-DNO_DOCS=ON \
-	-DFBSUPPORT=OFF \
 	-DCMAKE_PREFIX_PATH:UNINITIALIZED="$QT5_ANDROID_CMAKE" \
 	-DCMAKE_BUILD_TYPE="$BUILD_TYPE" \
 	-DMAKE_TESTS=OFF \

packaging/ios/Subsurface-mobile.pro

@@ -29,9 +29,7 @@ SOURCES += ../../subsurface-mobile-main.cpp \
 	../../core/exif.cpp \
 	../../core/format.cpp \
 	../../core/gettextfromc.cpp \
-	../../core/isocialnetworkintegration.cpp \
 	../../core/metrics.cpp \
-	../../core/pluginmanager.cpp \
 	../../core/qt-init.cpp \
 	../../core/subsurfacesysinfo.cpp \
 	../../core/windowtitleupdate.cpp \
@@ -82,7 +80,6 @@ SOURCES += ../../subsurface-mobile-main.cpp \
 	../../core/settings/qPrefDisplay.cpp \
 	../../core/settings/qPrefDiveComputer.cpp \
 	../../core/settings/qPrefDivePlanner.cpp \
-	../../core/settings/qPrefFacebook.cpp \
 	../../core/settings/qPrefGeneral.cpp \
 	../../core/settings/qPrefGeocoding.cpp \
 	../../core/settings/qPrefLanguage.cpp \
@@ -178,10 +175,8 @@ HEADERS += \
 	../../core/gaspressures.h \
 	../../core/gettext.h \
 	../../core/gettextfromc.h \
-	../../core/isocialnetworkintegration.h \
 	../../core/membuffer.h \
 	../../core/metrics.h \
-	../../core/pluginmanager.h \
 	../../core/qt-gui.h \
 	../../core/sha1.h \
 	../../core/strndup.h \
@@ -202,7 +197,6 @@ HEADERS += \
 	../../core/settings/qPrefDisplay.h \
 	../../core/settings/qPrefDiveComputer.h \
 	../../core/settings/qPrefDivePlanner.h \
-	../../core/settings/qPrefFacebook.h \
 	../../core/settings/qPrefGeneral.h \
 	../../core/settings/qPrefGeocoding.h \
 	../../core/settings/qPrefLanguage.h \