Use tde_conditional_add_project_… rules #3

This PR is in two parts:
1] Update to use tde_conditional_add_project_… rules for documentation and translations.

2] Set macro calls for .desktop files in a single top level file.

1] commit ba15b70b2

Removed CMakeLists.txt from doc & translations
Moved doc/en/index.docbook to doc/en/kcontrol
Deleted and added macro calls in top level CMakeLists.txt

2] commit 0eb60aeae
Having all the macro calls in a single top level file will be easier for setting up and administering the parameters. This will also fit well with the concept of cmake common rules having a single point for the function calls.

For knemo, there are only two .desktop files and the eventsrc file and it's therefore a simple example of what could be done.

There are a lot of .desktop files to be generated for amarok, and this will be a lot easier than setting up the tde_create_translated_desktop() macro calls in the individual CMakeLists.txt.

The first part is without discussion – it is good, ready for merging.

For the second part I hesitate. For me, it seems correct that desktop files are located in the directory to which part belongs. And also that they are processed in CMakeLists, which corresponds to the part in which it belongs to. For example, thank to this it will naturally be conditioned by the options like WITH_... or BUILD_..., which may apply to the appropriate part. Desktop files are more bound to code than translations and documentation. In any case, your arguments also seem appropriate. This will need more discussion.

Regarding the second part, I agree with Slavek. Let's not forget that this is a simple and small module, but there are others which have hundreds of desktop files (think tdebase, tdelibs, tdepims for example). There those desktop files are often related to different things/modules, so having separate location and cmake rules makes perfect sense. And for the sake of consistency, it would be better to follow the same rules acroos all TDE project.

Rebased to current head, commit 0eb60aeae removed from PR.