refactoring networking; adding network interface

todo: adjusting tests
disabled network tests; reordered import headers

todo: mocking networking tests
fixing and extending docu for netio::Manager
adding docu for AuthInfo stuff
fixing and adding file header comments
add/extend docu for netio::Error
add docu to netio::ModifiedInfo

+ replace Qt macros by custom ones
+ fix non-virtual destructor for Manager
fix Network::buildRequest Authorization construction

* not not true is true not false
* in case no credentials are given, don't add Authorization header
adding GoogleTest and GoogleMock as dependencies

for now Git-Mirrors of cpp-netlib are used

todo: switch to more maintained versions
including gtest and gmock as shared libs
adjust travis to new submodules
remove additional out-of-cmake build for travis

[skip ci]
gtest+gmock as shared --> segfault
piping Response details through INetwork

todo: probably undo this at a later stage
initial implementation of NetworkMock

not yet working

[skip ci]
switching to own gtest/gmock mirrors
final switch to own mirrors
fixing ManagerTest
adding -Wall flag to debug mode
always work with pointers for QNetworkReply and INetwork

there should be only one instance of each at all times

todo: use shared_pointers for this