Adapt to the merge of profilesconfig and globalconfig KCMs,and remove "backend" terminology where it may be confusing.
ProfileConfigKCM->PowerKCMProfileConfigData->PowerConfigDatabackendCharge*Threshold->savedCharge*Threshold
The external name of the KCM is not changed in this commit.
Note for reviewers: I think it also makes sense to merge kcmodule/common/ and kcmodule/profile/ directories into a single one (perhaps just kcm/) but that can be another commit involving only file moves & no changes in C++ files.