CppTools: rewriting tests for include hierarchy

Now include hierarchy model is printed as a string
represantation and can be easily compared to expected
situation.

Change-Id: I6aeff860744710015c5891ad0db4fdb62942f1cd
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>
CppTools: fix infinite deep tree for "Included by"

"Included by" was infected by infinite deep tree in case of cyclic.

Change-Id: If84fe52399f49d52baa42d681ab125d10d89dd3e
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>
CppTools: fix showing cyclic in a wrong level of IncludeHierarchy

File path for which we build hierarchy was not consider in cyclic checking.

Added tests for cyclic cases

Change-Id: I0c2e60034c6e8f3aa69ab723350b4c05530fcdfb
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>